Methods and Devices for Optically Determining A Characteristic of a Substance

ABSTRACT

Optical computing devices are disclosed. One exemplary optical computing device includes an electromagnetic radiation source configured to optically interact with a sample and first and second integrated computational elements arranged in primary and reference channels, respectively, the first and second computational elements are configured to be either positively or negatively correlated to the characteristic of the sample. The first and second integrated computational elements produce first and second modified electromagnetic radiations, and a detector is arranged to receive the first and second modified electromagnetic radiations and generate an output signal corresponding to the characteristic of the sample.

BACKGROUND

The present invention generally relates to systems and methods ofoptical computing and, more specifically, to systems and methods ofdetermining a particular characteristic of a substance using two or moreintegrated computational elements.

Spectroscopic techniques for measuring various characteristics ofmaterials are well known and are routinely used under laboratoryconditions. In some cases, these spectroscopic techniques can be carriedout without using an involved sample preparation. It is more common,however, to carry out various sample preparation steps before conductingthe analysis. Reasons for conducting sample preparation steps caninclude, for example, removing interfering background materials from theanalyte of interest, converting the analyte of interest into a chemicalform that can be better detected by the chosen spectroscopic technique,and adding standards to improve the accuracy of quantitativemeasurements. Thus, there is usually a delay in obtaining an analysisdue to sample preparation time, even discounting the transit time oftransporting the sample to a laboratory.

Although spectroscopic techniques can, at least in principle, beconducted at a job site or in a process, the foregoing concernsregarding sample preparation times can still apply. Furthermore, thetransitioning of spectroscopic instruments from a laboratory into afield or process environment can be expensive and complex. Reasons forthese issues can include, for example, the need to overcome inconsistenttemperature, humidity, and vibration encountered during field or processuse. Furthermore, sample preparation, when required, can be difficultunder field analysis conditions. The difficulty of performing samplepreparation in the field can be especially problematic in the presenceof interfering materials, which can further complicate conventionalspectroscopic analyses. Quantitative spectroscopic measurements can beparticularly challenging in both field and laboratory settings due tothe need for precision and accuracy in sample preparation and spectralinterpretation.

SUMMARY OF THE INVENTION

The present invention generally relates to systems and methods ofoptical computing and, more specifically, to systems and methods ofdetermining a particular characteristic of a substance using two or moreintegrated computational elements.

Aspects of the present disclosure may provide a device including anelectromagnetic radiation source configured to optically interact with asample having a characteristic of interest; a first integratedcomputational element arranged within a primary channel and configuredto optically interact with the electromagnetic radiation source andproduce a first modified electromagnetic radiation, wherein the firstintegrated computational element is configured to be positively ornegatively correlated to the characteristic of interest; a secondintegrated computational element arranged within a reference channel andconfigured to optically interact with the electromagnetic radiationsource and produce a second modified electromagnetic radiation, whereinthe second integrated computational element is configured to bepositively or negatively correlated to the characteristic of interest;and a first detector arranged to receive the first and second modifiedelectromagnetic radiations from the first and second integratedcomputational elements, respectively, and generate an output signalcorresponding to the characteristic of the sample.

Aspects of the present disclosure may further provide a method ofdetermining a characteristic of a sample. The method may includeoptically interacting an electromagnetic radiation source with thesample and a first integrated computational element arranged within aprimary channel and a second integrated computational element arrangedwithin a reference channel, wherein the first and second computationalelements are configured to be positively or negatively correlated to thecharacteristic of the sample; producing first and second modifiedelectromagnetic radiations from the first and second integratedcomputational elements, respectively; receiving the first and secondmodified electromagnetic radiations with a first detector; andgenerating an output signal with the first detector, the output signalcorresponding to the characteristic of the sample.

Aspects of the present disclosure may also provide a device including anelectromagnetic radiation source configured to optically interact with asample having a characteristic of interest; a first integratedcomputational element arranged within a primary channel and configuredto optically interact with the electromagnetic radiation source andproduce a first modified electromagnetic radiation, wherein the firstintegrated computational element is configured to be positively ornegatively correlated to the characteristic of interest; a secondintegrated computational element arranged within a second channel andconfigured to optically interact with the electromagnetic radiationsource and produce a second modified electromagnetic radiation, whereinthe second integrated computational element is configured to bepositively or negatively correlated to the characteristic of interest; afirst detector arranged to receive the first modified electromagneticradiation and generate a first output signal; a second detector arrangedto receive the second modified electromagnetic radiation and generate asecond output signal; and a signal processor configured to receive andcomputationally combine the first and second output signals to determinethe characteristic of interest of the sample.

Aspects of the present disclosure may yet further provide another methodof determining a characteristic of a sample. The method may includeoptically interacting an electromagnetic radiation source with thesample and a first integrated computational element arranged within aprimary channel and a second integrated computational element arrangedwithin a reference channel, wherein the first and second computationalelements are configured to be positively or negatively correlated to thecharacteristic of the sample; producing first and second modifiedelectromagnetic radiations from the first and second integratedcomputational elements, respectively; receiving the first modifiedelectromagnetic radiation with a first detector; receiving the secondmodified electromagnetic radiation with a second detector; generating afirst output signal with the first detector and a second output signalwith the second detector; and computationally combining the first andsecond output with a signal processor to determine the characteristic ofinterest of the sample.

The features and advantages of the present invention will be readilyapparent to one having ordinary skill in the art upon a reading of thedescription of the preferred embodiments that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent invention, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modification,alteration, and equivalents in form and function, as will occur to onehaving ordinary skill in the art and having the benefit of thisdisclosure.

FIG. 1 illustrates an exemplary integrated computation element,according to one or more embodiments.

FIG. 2 a illustrates a block diagram non-mechanistically illustratinghow an optical computing device distinguishes electromagnetic radiationrelated to a characteristic of interest from other electromagneticradiation, according to one or more embodiments.

FIG. 2 b illustrates another block diagram non-mechanisticallyillustrating how an optical computing device distinguisheselectromagnetic radiation related to a characteristic of interest fromother electromagnetic radiation, according to one or more embodiments.

FIG. 3 a illustrates an exemplary optical computing device, according toone or more embodiments.

FIG. 3 b illustrates another exemplary optical computing device,according to one or more embodiments.

FIG. 4 a illustrates a graph indicating the detection of acharacteristic of interest in a sample using one or more integratedcomputational elements.

FIG. 4 b illustrates is a graph showing the calibration plots for theintegrated computational elements referenced in FIG. 4 a.

FIG. 4 c illustrates a graph that re-plots the graph of FIG. 4 a withcategorization of the integrated computational elements by theirpositive and negative natures.

FIG. 4 d provides a table that summarizes the tests of the fiveintegrated computational elements depicted in the graph of FIG. 4 c.

FIG. 6 illustrates another exemplary optical computing device, accordingto one or more embodiments.

FIG. 7 illustrates another exemplary optical computing device, accordingto one or more embodiments.

FIG. 8 illustrates another exemplary optical computing device, accordingto one or more embodiments.

FIG. 9 illustrates another exemplary optical computing device, accordingto one or more embodiments.

FIG. 10 illustrates another exemplary optical computing device,according to one or more embodiments.

FIG. 11 illustrates another exemplary optical computing device,according to one or more embodiments.

DETAILED DESCRIPTION

The present invention generally relates to systems and methods ofoptical computing and, more specifically, to systems and methods ofdetermining a particular characteristic of a substance using two or moreintegrated computational elements.

Embodiments described herein include various configurations of opticalcomputing devices, also commonly referred to as opticoanalyticaldevices. The various embodiments of the disclosed optical computingdevices may be suitable for use in the oil and gas industry. Forexample, embodiments disclosed herein provide systems and/or devicescapable of providing a relatively low cost, rugged, and accurate systemfor monitoring petroleum quality for the purpose of optimizing decisionmaking at a well site and efficient management of hydrocarbonproduction. Embodiments disclosed herein may also be useful indetermining concentrations of various analytes or characteristics ofinterest in hydrocarbons present within a wellbore. Embodimentsdisclosed herein may also be useful in determining concentrations ofvarious analytes of interest in other fluids, such as water, importantin the oil and gas industry. It will be appreciated, however, that thevarious disclosed systems and devices are equally applicable to othertechnology fields including, but not limited to, the food and drugindustry, industrial applications, mining industries, or any field whereit may be advantageous to determine in real-time the concentrations of aspecific character or analyte of interest of a compound or material.

As used herein, the term “fluid” refers to any substance that is capableof flowing, including particulate solids, liquids, gases, slurries,emulsions, powders, muds, glasses, combinations thereof, and the like.In some embodiments, the fluid can be an aqueous fluid, including wateror the like. In some embodiments, the fluid can be a non-aqueous fluid,including organic compounds, more specifically, hydrocarbons, oil, arefined component of oil, petrochemical products, and the like. In someembodiments, the fluid can be a treatment fluid or a formation fluid.Fluids can include various flowable mixtures of solids, liquid and/orgases. Illustrative gases that can be considered fluids according to thepresent embodiments include, for example, air, nitrogen, carbon dioxide,argon, helium, hydrogen disulfide, mercaptan, thiophene, methane,ethane, butane, and other hydrocarbon gases, and/or the like.

As used herein, the term “characteristic” refers to a chemical,mechanical, or physical property of a substance. A characteristic of asubstance may include a quantitative value of one or more chemicalcomponents therein. Such chemical components may be referred to as“analytes.” Illustrative characteristics of a substance that can bemonitored with the optical computing devices disclosed herein caninclude, for example, chemical composition (identity and concentration,in total or of individual components), impurity content, pH, viscosity,density, ionic strength, total dissolved solids, salt content, porosity,opacity, bacteria content, combinations thereof, and the like.

As used herein, the term “electromagnetic radiation” refers to radiowaves, microwave radiation, infrared and near-infrared radiation,visible light, ultraviolet light, X-ray radiation and gamma rayradiation.

As used herein, the term “optical computing device” refers to an opticaldevice that is configured to receive an input of electromagneticradiation from a substance or sample of the substance and produce anoutput of electromagnetic radiation from a processing element. Theprocessing element may be, for example, an integrated computationalelement. The electromagnetic radiation emanating from the processingelement is changed in some way so as to be readable by a detector, suchthat an output of the detector can be correlated to at least onecharacteristic of the substance. The output of electromagnetic radiationfrom the processing element can be reflected electromagnetic radiation,transmitted electromagnetic radiation, and/or dispersed electromagneticradiation. As will be appreciated by those skilled in the art, whetherreflected or transmitted electromagnetic radiation is analyzed by thedetector will be a matter of routine experimental design. In addition,emission and/or scattering of the substance, for example viafluorescence, luminescence, radiation and re-radiation, Ramanscattering, and/or Raleigh scattering can also be monitored by theoptical computing devices.

As used herein, the term “optically-interact” or variations thereofrefers to the reflection, transmission, scattering, diffraction,radiating, re-radiating, or absorption of electromagnetic radiationeither on, through, or from one or more processing elements, such asintegrated computational elements. Accordingly, optically-interactedlight refers to light that has been reflected, transmitted, scattered,diffracted, or absorbed by, emitted, radiated or re-radiated, forexample, using the integrated computational elements, but may also applyto interaction with a sample substance.

As used herein, the term “sample,” or variations thereof, refers to atleast a portion of a substance of interest to be tested or otherwiseevaluated using the optical computing devices described herein. Thesample includes the characteristic of interest, as defined above, andmay be any fluid, as defined herein, or otherwise any solid substance ormaterial such as, but not limited to, rock formations, concrete, othersolid surfaces, etc.

At the very least, the exemplary optical computing devices disclosedherein will each include an electromagnetic radiation source, at leasttwo processing elements (e.g., integrated computational elements), andat least one detector arranged to receive optically-interacted lightfrom the at least two processing elements. As disclosed below, however,in at least one embodiment, the electromagnetic radiation source may beomitted and instead the electromagnetic radiation may be derived fromthe substance or the sample of the substance itself. In someembodiments, the exemplary optical computing devices may be specificallyconfigured for detecting, analyzing, and quantitatively measuring aparticular characteristic or analyte of interest of a given sample orsubstance. In other embodiments, the exemplary optical computing devicesmay be general purpose optical devices, with post-acquisition processing(e.g., through computer means) being used to specifically detect thecharacteristic of the sample.

In some embodiments, suitable structural components for the exemplaryoptical computing devices disclosed herein are described in commonlyowned U.S. Pat. Nos. 6,198,531; 6,529,276; 7,123,844; 7,834,999;7,911,605, 7,920,258, and 8,049,881, each of which is incorporatedherein by reference in its entirety, and U.S. patent application Ser.Nos. 12/094,460 (U.S. Pat. App. Pub. No. 2009/0219538); and 12/094,465(U.S. Pat. App. Pub. No. 2009/0219539), each of which is alsoincorporated herein by reference in its entirety. As will beappreciated, variations of the structural components of the opticalcomputing devices described in the above-referenced patents and patentapplications may be suitable, without departing from the scope of thedisclosure, and therefore should not be considered limiting to thevarious embodiments disclosed herein.

The optical computing devices described in the foregoing patents andpatent applications combine the advantage of the power, precision andaccuracy associated with laboratory spectrometers, while being extremelyrugged and suitable for field use. Furthermore, the optical computingdevices can perform calculations (analyses) in real-time or nearreal-time without the need for sample processing. In this regard, theoptical computing devices can be specifically configured to detect andanalyze particular characteristics and/or analytes of interest. As aresult, interfering signals are discriminated from those of interest ina sample by appropriate configuration of the optical computing devices,such that the optical computing devices provide a rapid responseregarding the characteristics of the sample as based on the detectedoutput. In some embodiments, the detected output can be converted into avoltage that is distinctive of the magnitude of the characteristic beingmonitored in the sample. The foregoing advantages and others make theoptical computing devices, and their variations generally describedbelow, particularly well suited for field and downhole use.

The exemplary optical computing devices described herein can beconfigured to detect not only the composition and concentrations of amaterial or mixture of materials, but they also can be configured todetermine physical properties and other characteristics of the materialas well, based on their analysis of the electromagnetic radiationreceived from the sample. For example, the optical computing devices canbe configured to determine the concentration of an analyte and correlatethe determined concentration to a characteristic of a substance by usingsuitable processing means. As will be appreciated, the optical computingdevices may be configured to detect as many characteristics or analytesas desired in a given sample. All that is required to accomplish themonitoring of multiple characteristics or analytes is the incorporationof suitable processing and detection means within the optical computingdevice for each characteristic or analyte. In some embodiments, theproperties of a substance can be a combination of the properties of theanalytes therein (e.g., a linear, non-linear, logarithmic, and/orexponential combination). Accordingly, the more characteristics andanalytes that are detected and analyzed using the exemplary opticalcomputing devices, the more accurately the properties of the givensample can be determined.

Fundamentally, optical computing devices utilize electromagneticradiation to perform calculations, as opposed to the hardwired circuitsof conventional electronic processors. When electromagnetic radiationinteracts with a substance, unique physical and chemical informationabout the substance is encoded in the electromagnetic radiation that isreflected from, transmitted through, or radiated from the sample. Thisinformation is often referred to as the substance's spectral“fingerprint.” The exemplary optical computing devices disclosed hereinare capable of extracting the information of the spectral fingerprint ofmultiple characteristics or analytes within a substance and convertingthat information into a detectable output regarding the overallproperties of a sample. That is, through suitable configurations of theexemplary optical computing devices, electromagnetic radiationassociated with characteristics or analytes of interest in a substancecan be separated from electromagnetic radiation associated with allother components of a sample in order to estimate the sample'sproperties in real-time or near real-time.

The at least two processing elements used in the exemplary opticalcomputing devices described herein may be characterized as integratedcomputational elements (ICE). The ICE are capable of distinguishingelectromagnetic radiation related to the characteristic or analyte ofinterest from electromagnetic radiation related to other components of asample substance. Referring to FIG. 1, illustrated is an exemplary ICE100 suitable for use in the various optical computing devices describedherein, according to one or more embodiments. As illustrated, the ICE100 may include a plurality of alternating layers 102 and 104, such assilicon (Si) and SiO₂ (quartz), respectively. In general, these layersconsist of materials whose index of refraction is high and low,respectively. Other examples might include niobia and niobium, germaniumand germania, MgF, SiO, and other high and low index materials as knownin the art. The layers 102, 104 may be strategically deposited on anoptical substrate 106. In some embodiments, the optical substrate 106 isBK-7 optical glass. In other embodiments, the optical substrate 106 maybe other types of optical substrates, such as quartz, sapphire, silicon,germanium, zinc selenide, zinc sulfide, or various plastics such aspolycarbonate, polymethalmethacrylate PMMA), polyvinylchloride (PVC),diamond, ceramics, etc., as known in the art.

At the opposite end (e.g., opposite the optical substrate 106), the ICE100 may include a layer 108 that is generally exposed to the environmentof the device or installation. The number of layers 102, 104 and thethickness of each layer 102, 104 are determined from the spectralattributes acquired from a spectroscopic analysis of a characteristic ofthe sample substance using a conventional spectroscopic instrument. Thespectrum of interest of a given characteristic of a sample typicallyincludes any number of different wavelengths. It should be understoodthat the exemplary ICE 100 in FIG. 1 does not in fact represent anyparticular characteristic of a given sample, but is provided forpurposes of illustration only. Consequently, the number of layers 102,104 and their relative thicknesses, as shown in FIG. 1, bear nocorrelation to any particular characteristic of a given sample. Nor arethe layers 102, 104 and their relative thicknesses necessarily drawn toscale, and therefore should not be considered limiting of the presentdisclosure. Moreover, those skilled in the art will readily recognizethat the materials that make up each layer 102, 104 (i.e., Si and SiO₂)may vary, depending on the application, cost of materials, and/orapplicability of the material to the sample substance. For example, thelayers 102, 104 may be made of, but are not limited to, silicon,germanium, water, combinations thereof, or other materials of interest.

In some embodiments, the material of each layer 102, 104 can be doped ortwo or more materials can be combined in a manner to achieve the desiredoptical characteristic. In addition to solids, the exemplary ICE 100 mayalso contain liquids and/or gases, optionally in combination withsolids, in order to produce a desired optical characteristic. In thecase of gases and liquids, the ICE 100 can contain a correspondingvessel (not shown) which houses the gases or liquids. Exemplaryvariations of the ICE 100 may also include holographic optical elements,gratings, piezoelectric, light pipe, digital light pipe (DLP), and/oracousto-optic elements, for example, that can create transmission,reflection, and/or absorptive properties of interest.

The multiple layers 102, 104 exhibit different refractive indices. Byproperly selecting the materials of the layers 102, 104 and theirrelative spacing, the exemplary ICE 100 may be configured to selectivelypass/reflect/refract predetermined fractions of light (i.e.,electromagnetic radiation) at different wavelengths. Each wavelength isgiven a predetermined weighting or loading factor. The thicknesses andspacing of the layers 102, 104 may be determined using a variety ofapproximation methods from the spectrograph of the character or analyteof interest. These methods may include inverse Fourier transform (IFT)of the optical transmission spectrum and structuring the ICE 100 as thephysical representation of the IFT. The approximations convert the IFTinto a structure based on known materials with constant refractiveindices. Further information regarding the structures and design ofexemplary integrated computational elements (also referred to asmultivariate optical elements) is provided in Applied Optics, Vol. 35,pp. 5484-5492 (1996) and Vol. 129, pp. 2876-2893, which is incorporatedby reference herein to the extent not inconsistent with the presentdisclosure.

The weightings that the layers 102, 104 of the ICE 100 apply at eachwavelength are set to the regression weightings described with respectto a known equation, or data, or spectral signature. For example, theICE 100 may be configured to perform the dot product of the input lightbeam into the ICE 100 and a desired loaded regression vector representedby each layer 102, 104 for each wavelength. As a result, the outputlight intensity of the ICE 100 is related to the characteristic oranalyte of interest.

As further explanation, accurately determining the regression vector ofthe characteristic of interest in the sample provides a means for theoptical computing devices generally described herein to determine orotherwise calculate a concentration of said characteristic in thesample. The regression vector for each characteristic may be determinedusing standard procedures that will be familiar to one having ordinaryskill in the art. For example, in various embodiments, analyzing thespectrum of the sample may include determining a dot product of theregression vector for each characteristic of the sample being analyzed.As one of ordinary skill in art will recognize, a dot product of avector is a scalar quantity (i.e., a real number). While the dot productvalue is believed to have no physical meaning by itself (e.g., it mayreturn a positive or negative result of any magnitude), comparison ofthe dot product value of a sample with dot product values obtained forknown reference standards and plotted in a calibration curve may allowthe sample dot product value to be correlated with a concentration orvalue of a characteristic, thereby allowing unknown samples to beaccurately analyzed.

To determine the dot product, one simply multiples the regressioncoefficient of the regression vector at a given wavelength times thespectral intensity at the same wavelength. This process is repeated forall wavelengths analyzed, and the products are summed over the entirewavelength range to yield the dot product. Those skilled in the art willrecognize that two or more characteristics may be determined from asingle spectrum of the sample by applying a corresponding regressionvector for each characteristic.

In practice it is possible to derive information from electromagneticradiation interacting with a sample by, for example, separating theelectromagnetic radiation from several samples into wavelength bands andperforming a multiple linear regression of the band intensity against acharacteristic of interest determined by another measurement techniquefor each sample. The measured characteristic may be expressed andmodeled by multiple linear regression techniques that will be familiarto one having ordinary skill in the art. Specifically, if y is themeasured value of the concentration or characteristic, y may beexpressed as in Formula 1:

y=a ₀ +a ₁ w ₁ +a ₂ w ₂ +a ₃ w ₃ +a ₄ w ₄+  (Formula 1)

where each a is a constant determined by the regression analysis andeach w is the light intensity for each wavelength band. Depending on thecircumstances, the estimate obtained from Formula 1 may be inaccurate,for example, due to the presence of other characteristics within thesample that may affect the intensity of the wavelength bands.

A more accurate estimate may be obtained by expressing theelectromagnetic radiation in terms of its principal components. Toobtain the principal components, spectroscopic data is collected for avariety of similar samples using the same type of electromagneticradiation. For example, following exposure to each sample, theelectromagnetic radiation may be collected and the spectral intensity ateach wavelength may be measured for each sample. This data may then bepooled and subjected to a linear-algebraic process known as singularvalue decomposition (SVD) in order to determine the principalcomponents. Use of SVD in principal component analysis will be wellunderstood by one having ordinary skill in the art. Briefly, principalcomponent analysis is a dimension reduction technique, which takes mspectra with n independent variables and constructs a new set ofeigenvectors that are linear combinations of the original variables. Theeigenvectors may be considered a new set of plotting axes. The primaryaxis, termed the first principal component, is the vector that describesmost of the data variability. Subsequent principal components describesuccessively less sample variability, until the higher order principalcomponents essentially describe only spectral noise.

Typically, the principal components are determined as normalizedvectors. Thus, each component of an electromagnetic radiation sample maybe expressed as x_(n)z_(n), where x_(n) is a scalar multiplier and z_(n)is the normalized component vector for the n_(th) component. That is,z_(n) is a vector in a multi-dimensional space where each wavelength isa dimension. Normalization determines values for a component at eachwavelength so that the component maintains its shape and the length ofthe principal component vector is equal to one. Thus, each normalizedcomponent vector has a shape and a magnitude so that the components maybe used as the basic building blocks of any electromagnetic radiationsample having those principal components. Accordingly, eachelectromagnetic radiation sample may be described by a combination ofthe normalized principal components multiplied by the appropriate scalarmultipliers, as set forth in Formula 2:

x ₁ z ₁ +x ₂ z ₂ +. . . +x _(n) z _(n)  (Formula 2)

The scalar multipliers x_(n) may be considered the “magnitudes” of theprincipal components in a given electromagnetic radiation sample whenthe principal components are understood to have a standardized magnitudeas provided by normalization.

Because the principal components are orthogonal, they may be used in arelatively straightforward mathematical procedure to decompose anelectromagnetic radiation sample into the component magnitudes, whichmay accurately describe the data in the original electromagneticradiation sample. Since the original electromagnetic radiation samplemay also be considered a vector in the multi-dimensional wavelengthspace, the dot product of the original signal vector with a principalcomponent vector is the magnitude of the original signal in thedirection of the normalized component vector. That is, it is themagnitude of the normalized principal component present in the originalsignal. This is analogous to breaking a vector in a three dimensionalCartesian space into its X, Y and Z components. The dot product of thethree-dimensional vector with each axis vector, assuming each axisvector has a magnitude of 1, gives the magnitude of the threedimensional vector in each of the three directions. The dot product ofthe original signal and some other vector that is not perpendicular tothe other three dimensions provides redundant data, since this magnitudeis already contributed by two or more of the orthogonal axes.

Because the principal components are orthogonal (i.e., perpendicular) toeach other, the dot product of any principal component with any otherprincipal component is zero. Physically, this means that the componentsdo not interfere with each other. If data is altered to change themagnitude of one component in the original electromagnetic radiationsignal, the other components remain unchanged. In the analogousCartesian example, reduction of the X component of the three dimensionalvector does not affect the magnitudes of the Y and Z components.

Principal component analysis provides the fewest orthogonal componentsthat can accurately describe the data carried by the electromagneticradiation samples. Thus, in a mathematical sense, the principalcomponents are components of the original electromagnetic radiation thatdo not interfere with each other and that represent the most compactdescription of the spectral signal. Physically, each principal componentis an electromagnetic radiation signal that forms a part of the originalelectromagnetic radiation signal. Each principal component has a shapeover some wavelength range within the original wavelength range. Summingthe principal components may produce the original signal, provided eachcomponent has the proper magnitude, whether positive or negative.

The principal components may comprise a compression of the informationcarried by the total light signal. In a physical sense, the shape andwavelength range of the principal components describe what informationis in the total electromagnetic radiation signal, and the magnitude ofeach component describes how much of that information is present. Ifseveral electromagnetic radiation samples contain the same types ofinformation, but in differing amounts, then a single set of principalcomponents may be used to describe (except for noise) eachelectromagnetic radiation sample by applying appropriate magnitudes tothe components. The principal components may be used to provide anestimate of the characteristic of the sample based upon the informationcarried by the electromagnetic radiation that has interacted with thatsample. Differences observed in spectra of samples having varyingquantities of a constituent or values of a characteristic may bedescribed as differences in the magnitudes of the principal components.Thus, the concentration of the characteristic may be expressed by theprincipal components according to Formula 3 in the case where fourprincipal components are used:

y=a ₀ +a ₁ x ₁ +a ₂ x ₂ +a ₃ x ₃ +a ₄ x ₄  (Formula 3)

where y is a concentration or value of a characteristic, each a is aconstant determined by the regression analysis, and x₁, x₂, x₃ and x₄are the first, second, third, and fourth principal component magnitudes,respectively. Formula 3 may be referred to as a regression vector. Theregression vector may be used to provide an estimate for theconcentration or value of the characteristic for an unknown sample.

Regression vector calculations may be performed by computer, based onspectrograph measurements of electromagnetic radiation by wavelength.The spectrograph system spreads the electromagnetic radiation into itsspectrum and measures the spectral intensity at each wavelength over thewavelength range. Using Formula 3, the computer may read the intensitydata and decompose the electromagnetic radiation sample into theprincipal component magnitudes x_(n) by determining the dot product ofthe total signal with each component. The component magnitudes are thenapplied to the regression equation to determine a concentration or valueof the characteristic.

To simplify the foregoing procedure, however, the regression vector maybe converted to a form that is a function of wavelength so that only onedot product is determined. Each normalized principal component vectorz_(n) has a value over all or part of the total wavelength range. Ifeach wavelength value of each component vector is multiplied by theregression constant a_(n) corresponding to the component vector, and ifthe resulting weighted principal components are summed by wavelength,the regression vector takes the form of Formula 4:

y=a ₀ +b ₁ u ₁ +b ₂ u ₂ +. . . +b _(n) u _(n)  (Formula 4)

where a₀ is the first regression constant from Formula 3, b_(n) is thesum of the multiple of each regression constant a_(n) from Formula 3 andthe value of its respective normalized regression vector at wavelengthn, and u_(n) is the intensity of the electromagnetic radiation atwavelength n. Thus, the new constants define a vector in wavelengthspace that directly describes a concentration or characteristic of asample. The regression vector in the form of Formula 4 represents thedot product of an electromagnetic radiation sample with this vector.

Normalization of the principal components provides the components withan arbitrary value for use during the regression analysis. Accordingly,it is very unlikely that the dot product value produced by theregression vector will be equal to the actual concentration orcharacteristic value of a sample being analyzed. The dot product resultis, however, proportional to the concentration or characteristic value.As discussed above, the proportionality factor may be determined bymeasuring one or more known calibration samples by conventional meansand comparing the result to the dot product value of the regressionvector. Thereafter, the dot product result can be compared to the valueobtained from the calibration standards in order to determine theconcentration or characteristic of an unknown sample being analyzed.

The exemplary optical computing devices described herein are powerfulpredictive spectroscopic devices that incorporate a multi-wavelengthspectral weighting directly into analytical instrumentation. Furtherdetails regarding how the exemplary ICE 100 is able to separate andprocess electromagnetic radiation related to the characteristic oranalyte of interest is described below described in U.S. Pat. Nos.6,198,531; 6,529,276; and 7,920,258, previously incorporated herein byreference.

Referring now to FIG. 2 a, illustrated is a block diagram thatnon-mechanistically illustrates how an optical computing device 200 isable to distinguish electromagnetic radiation related to acharacteristic of a sample 202 from other electromagnetic radiation. Asshown in FIG. 2 a, an electromagnetic radiation source 201 emits orotherwise generates electromagnetic radiation 204. The electromagneticradiation source 201 may be any device capable of emitting or generatingelectromagnetic radiation, as defined herein. In some embodiments, theelectromagnetic radiation source 201 is a light bulb, light emittingdevice (LED), laser, blackbody, photonic crystal, or X-Ray source, orthe like. The electromagnetic radiation 204 is directed toward thesample 202, which contains an analyte of interest (e.g., acharacteristic of the sample) desired to be determined. Theelectromagnetic radiation 204 optically interacts with the sample 202and produces optically interacted radiation 206 (e.g., sample-interactedlight), some of which may be electromagnetic radiation corresponding tothe characteristic or analyte of interest and some of which may bebackground electromagnetic radiation corresponding to other componentsor characteristics of the sample 202.

While FIG. 2 a shows the electromagnetic radiation 204 as passingthrough the sample 202 to produce the optically interacted radiation206, it is also contemplated herein to reflect the electromagneticradiation 204 off of the sample 202, such as may be required when thesample 202 is translucent, opaque, or solid. Accordingly, reflecting theelectromagnetic radiation 204 off of the sample 202 also generates theoptically interacted radiation 206. Moreover, in some embodiments, theelectromagnetic radiation source 201 may be omitted altogether and therequired electromagnetic radiation may be derived from the sample 202itself. For example, various substances naturally radiateelectromagnetic radiation. For instance, the sample 202 may be ablackbody radiating substance configured to radiate electromagneticradiation in the form of heat. In other embodiments, the sample 202 maybe radioactive or chemo-luminescent and therefore radiateelectromagnetic radiation. In yet other embodiments, the requiredelectromagnetic radiation may be induced from the sample 202 by beingacted upon mechanically, magnetically, electrically, combinationsthereof, or the like.

Although not specifically shown, one or more spectral elements may beemployed in the device 200 in various locations in order to restrict theoptical wavelengths and/or bandwidths of the system and therebyeliminate unwanted electromagnetic radiation existing in wavelengthregions that have no importance. Such spectral elements can be locatedanywhere along the optical train, but are typically employed directlyafter the electromagnetic radiation source 201. Various configurationsand applications of spectral elements in optical computing devices maybe found in commonly owned U.S. Pat. Nos. 6,198,531; 6,529,276;7,123,844; 7,834,999; 7,711,605, 7,920,258, 8,049,881, and U.S. patentapplication Ser. Nos. 12/094,460 (U.S. Pat. App. Pub. No. 2009/0219538);12/094,465 (U.S. Pat. App. Pub. No. 2009/0219539), incorporated hereinby reference, as indicated above.

The optically interacted radiation 206 may impinge upon the opticalcomputing device 200, which may contain, for example, a beam splitter208. The beam splitter 208 may be configured to split the opticallyinteracted radiation 206 into a first beam of light 206 a directed in afirst channel A and a second beam of light 206 b directed in a secondchannel B. As used herein, the term “channel” refers generally to anoptical path or optical train, as known in the art. The first channel Ais configured to direct the first beam of light 206 a toward an ICE 209,thus the first channel A may be characterized as or otherwise called a“primary” channel. The ICE 209 may be substantially similar to the ICE100 described above with reference to FIG. 1. The ICE 209 may beconfigured to produce modified electromagnetic radiation 210corresponding to the characteristic or analyte of interest. Inparticular, the modified electromagnetic radiation 210 may includeelectromagnetic radiation that has optically interacted with the ICE209, whereby an approximate mimicking of the regression vectorcorresponding to the characteristic of interest is obtained.

Within the primary channel A, the modified electromagnetic radiation 210is subsequently conveyed to a detector 212 for quantification. Thedetector 212 may be any device capable of detecting electromagneticradiation, and may be generally characterized as an optical transducer.For example, the detector 212 may be, but is not limited to, a thermaldetector such as a thermopile or photoacoustic detector, a semiconductordetector, a piezo-electric detector, a charge coupled device (CCD)detector, a video or array detector, a split detector, a photon detector(such as a photomultiplier tube), photodiodes, and/or combinationsthereof, or the like, or other detectors known to those skilled in theart.

In some embodiments, the detector 212 is configured to produce an outputsignal 213 in the form of a voltage (or current) that corresponds to theparticular characteristic of the sample 202. The voltage returned isessentially the dot product of the optical interaction of the first beamof light 206 a with the first ICE 209 as a function of the concentrationof the characteristic of interest of the sample 202. As such, the outputsignal 213 produced by the detector 212 and the concentration of thecharacteristic of the sample 202 may be directly proportional. In otherembodiments, however, the relationship may correspond to a polynomialfunction, an exponential function, a logarithmic function, and/or acombination thereof. In some embodiments, the ICE 209 may be configuredto be positively correlated, meaning that the voltage of the outputsignal 213 would tend to increase as the concentration of thecharacteristic of interest increases. In other embodiments, however, theICE 209 may be configured to be negatively correlated, meaning that thevoltage of the output signal 213 would tend to decrease as theconcentration of the characteristic of interest increases.

The second beam of light 206 b may be directed within the second channelB toward a second detector 216. The second detector 216 may be similarto the first detector 212, such as by being any device capable ofdetecting electromagnetic radiation. Without limitation, the seconddetector 216 may be used to detect radiating deviations stemming fromthe electromagnetic radiation source 201. Undesirable radiatingdeviations can occur in the intensity of the light in the primarychannel A due to a wide variety of reasons and potentially causingvarious negative effects. These negative effects can be particularlydetrimental for measurements taken over a period of time. Radiatingdeviations can include, for example, light intensity fluctuations of theelectromagnetic radiation 204. It can also include interferentfluctuations, which may scatter or absorb light from the sample 202 asit moves through the interaction space as might occur if a foreignsubstance such as dirt or dust is entrained within the sample 202 orotherwise passes in front of the electromagnetic radiation source 201.Radiating deviations can also include a film of material build-up on thewindows of the interrogation space which has the effect of reducing theamount of light ultimately reaching the detector 216. Without propercompensation, such radiating deviations could result in false readingsfrom the primary channel A, and the output signal 213 would no longer beprimarily related to the characteristic of interest.

To correct or compensate for these types of undesirable effects, thesecond detector 216 arranged in the second channel B may be configuredto generate a compensating signal 218 generally indicative of theradiating deviations of the electromagnetic radiation source 201, andthereby normalize the output signal 213. Accordingly, the second channelB may be typically characterized as or otherwise referred to a“reference” channel. In some applications, the compensating signal 218derived from the reference channel B and the output signal 213 derivedfrom the primary channel A may be transmitted to or otherwise receivedby a signal processor 220 communicably coupled to both the detectors212, 216. The signal processor 220 may be a computer including anon-transitory machine-readable medium, as discussed in more detailbelow. The signal processor 220 may be configured to computationallycombine the compensating signal 218 with the output signal 213 in orderto normalize the output signal 213 in view of any radiating deviationsas detected by the second detector 216. In some embodiments,computationally combining the output and compensating signals 213, 218may entail computing a ratio of the two signals 213, 218, therebyessentially computing a ratio of the primary and reference channels Aand B (e.g., A/B).

It should be noted that the reference channel B is created in a mannerwhich does not detrimentally change the predictive characteristics ofthe ICE 209 arranged in the primary channel A. For example, if thebeamsplitter 208 were replaced with a spectral element (e.g., one whosetransmittance or reflectance has a variation with wavelength), then thespectral characteristics of the light incident upon the ICE 209 arrangedin the primary channel A would be altered, and the light emerging fromthe ICE 209 would have its spectral characteristics and intensitychanged from the original design, with a generally negative consequence.Viewed another way, a spectrally-active element would modify theintended transmission (or reflection) spectrum of the ICE 209 which wasoriginally and carefully designed to mimic the regression vectorassociated with the analyte or characteristic of interest. Thus, thereference channel B is generally created to detect a portion of thelight beam before striking the ICE 209. Spectrally neutral elements(e.g., elements whose transmittance, absorbance, and/or reflectance donot vary substantially with wavelength) are generally used to create thereference channel B. At least some spectrally neutral elements that maybe used are, but are not limited to, neutral density filters andbeamsplitters, partially transparent masks, front surface Fresnelreflections, combinations thereof, or similar components.

The signal processor 220 may also be configured to further process theoutput and compensating signals 213, 218 in order to provide additionalcharacterization information about the sample 202 being analyzed. Insome embodiments, the identification and concentration of each analytein the sample 202 can be used to predict certain physicalcharacteristics of the sample 202. For example, the bulk characteristicsof a sample 202 can be estimated by using a combination of theproperties conferred to the sample 202 by each analyte.

In some embodiments, the concentration of each analyte or the magnitudeof each characteristic determined using the optical computing device 200can be fed into an algorithm run by the signal processor 220. Thealgorithm may be configured to make predictions on how thecharacteristics of the sample 202 change if the concentrations of theanalytes are changed relative to one another. In some embodiments, thealgorithm produces an output that is readable by an operator who canconsider the results and make proper adjustments or take appropriateaction, if needed, based upon the output.

The algorithm can be part of an artificial neural network configured touse the concentration of each detected analyte in order to evaluate thecharacteristic(s) of the sample 202 and, if desired, predict how tomodify the sample 202 in order to alter its properties in a desired way.Illustrative but non-limiting artificial neural networks are describedin commonly owned U.S. patent application Ser. No. 11/986,763 (U.S.Patent App. Pub. No. 2009/0182693), which is incorporated herein byreference to the extent not inconsistent with the present disclosure. Itis to be recognized that an artificial neural network can be trainedusing samples having known concentrations, compositions, and/orproperties, thereby generating a virtual library. As the virtual libraryavailable to the artificial neural network becomes larger, the neuralnetwork can become more capable of accurately predicting thecharacteristics of a sample having any number of analytes presenttherein. Furthermore, with sufficient training, the artificial neuralnetwork can more accurately predict the characteristics of the sample,even in the presence of unknown analytes.

It is recognized that the various embodiments herein directed tocomputer control and artificial neural networks, including variousblocks, modules, elements, components, methods, and algorithms, can beimplemented using computer hardware, software, combinations thereof, andthe like. To illustrate this interchangeability of hardware andsoftware, various illustrative blocks, modules, elements, components,methods and algorithms have been described generally in terms of theirfunctionality. Whether such functionality is implemented as hardware orsoftware will depend upon the particular application and any imposeddesign constraints. For at least this reason, it is to be recognizedthat one of ordinary skill in the art can implement the describedfunctionality in a variety of ways for a particular application.Further, various components and blocks can be arranged in a differentorder or partitioned differently, for example, without departing fromthe scope of the embodiments expressly described.

Computer hardware used to implement the various illustrative blocks,modules, elements, components, methods, and algorithms described hereincan include a processor configured to execute one or more sequences ofinstructions, programming stances, or code stored on a non-transitory,computer-readable medium. The processor can be, for example, a generalpurpose microprocessor, a microcontroller, a digital signal processor,an application specific integrated circuit, a field programmable gatearray, a programmable logic device, a controller, a state machine, agated logic, discrete hardware components, an artificial neural network,or any like suitable entity that can perform calculations or othermanipulations of data. In some embodiments, computer hardware canfurther include elements such as, for example, a memory [e.g., randomaccess memory (RAM), flash memory, read only memory (ROM), programmableread only memory (PROM), erasable read only memory (EPROM)], registers,hard disks, removable disks, CD-ROMS, DVDs, or any other like suitablestorage device or medium.

Executable sequences described herein can be implemented with one ormore sequences of code contained in a memory. In some embodiments, suchcode can be read into the memory from another machine-readable medium.Execution of the sequences of instructions contained in the memory cancause a processor to perform the process steps described herein. One ormore processors in a multi-processing arrangement can also be employedto execute instruction sequences in the memory. In addition, hard-wiredcircuitry can be used in place of or in combination with softwareinstructions to implement various embodiments described herein. Thus,the present embodiments are not limited to any specific combination ofhardware and/or software.

As used herein, a machine-readable medium refers to any medium thatdirectly or indirectly provides instructions to a processor forexecution. A machine-readable medium can take on many forms including,for example, non-volatile media, volatile media, and transmission media.Non-volatile media can include, for example, optical and magnetic disks.Volatile media can include, for example, dynamic memory. Transmissionmedia can include, for example, coaxial cables, wire, fiber optics, andwires that form a bus. Common forms of machine-readable media caninclude, for example, floppy disks, flexible disks, hard disks, magnetictapes, other like magnetic media, CD-ROMs, DVDs, other like opticalmedia, punch cards, paper tapes and like physical media with patternedholes, RAM, ROM, PROM, EPROM and flash EPROM.

In some embodiments, the data collected using the optical computingdevices can be archived along with data associated with operationalparameters being logged at a job site. Evaluation of job performance canthen be assessed and improved for future operations or such informationcan be used to design subsequent operations. In addition, the data andinformation can be communicated (wired or wirelessly) to a remotelocation by a communication system (e.g., satellite communication orwide area network communication) for further analysis. The communicationsystem can also allow remote monitoring and operation of a process totake place. Automated control with a long-range communication system canfurther facilitate the performance of remote job operations. Inparticular, an artificial neural network can be used in some embodimentsto facilitate the performance of remote job operations. That is, remotejob operations can be conducted automatically in some embodiments. Inother embodiments, however, remote job operations can occur under directoperator control, where the operator is not at the job site.

Referring to FIG. 2 b, illustrated is an exemplary variation of theoptical computing device 200 described above with reference to FIG. 2 a.In FIG. 2 b, the beam splitter may be replaced with the ICE 209 whichnow essentially functions like a beam splitter. Specifically, theoptically interacted radiation 206 may impinge upon the ICE 209 whichmay be configured to transmit the modified electromagnetic radiation 210in the primary channel A and simultaneously reflect a second modifiedelectromagnetic radiation 222 in the reference channel B. Each of thefirst and second modified electromagnetic radiations 210, 222 maycorrespond to the characteristic or analyte of interest. In particular,the modified electromagnetic radiations 210, 222 may each includeelectromagnetic radiation that has optically interacted with the ICE209, whereby approximation mimicking of the regression vectorcorresponding to the characteristic of interest is obtained. In use,however, the signal from the reference channel B may be used tonormalize the signal from the primary channel A, as generally describedabove.

For instance, the first detector 212 receives the first modifiedelectromagnetic radiation 210 and provides the output signal 213 to thesignal processor 220, and the second detector 216 receives the secondmodified electromagnetic radiation 222 and provides the compensatingsignal 218 to the signal processor. The signal processor 220computationally combines the compensating signal 218 with the outputsignal 213 in order to normalize the output signal 213 in view of anyradiating deviations as detected by the second detector 216. In theillustrated embodiment, where the second modified electromagneticradiation 222 also provides an approximate mimicking of the regressionvector corresponding to the characteristic of interest, computationallycombining the output and compensating signals 213, 218 may entailcomputing a ratio of the output signal 210 and the sum of the outputsignal 210 and the compensating signal 218. In other words, the signalprocessor 220 may be configured to compute the ratio of the signalderived from the primary channel A and the sum of the signals derivedfrom both the primary and compensating channels A,B (i.e., A/(A+B)).

Referring now to FIG. 3 a, illustrated is another optical computingdevice 300 also configured to determine a characteristic of interest ofthe sample 202. The optical computing device 300 may be similar inseveral respects to the optical computing device 200 described abovewith reference to FIGS. 2 a and 2 b. Accordingly, the device 300 may bebest understood with reference to FIG. 2 a, where like numeralsrepresent like elements that will not be described again in detail.Similar to the device 200 discussed above, the optical computing device300 receives an output of optically interacted radiation 206 emittedfrom the sample 202 after the sample 202 has been illuminated withelectromagnetic radiation 204 from the electromagnetic radiation source201. Unlike the optical computing device 200, however, the opticalcomputing device 300 may include at least two ICEs, illustrated as afirst ICE 302 and a second ICE 304. The first and second ICE 302, 304may be generally similar in construction to the ICE 100 described abovewith reference to FIG. 1, but may also vary from each other depending onthe application.

For instance, in some embodiments, the first and second ICE 302, 304 maybe configured to be associated with a particular characteristic of thesample 202. In other words, the first and second ICE 302, 304 may beespecially designed in their respective layers, thicknesses, andmaterials so as to correspond with the spectral attributes associatedwith the characteristic of interest. Each of the first and second ICE302, 304, however, may be designed entirely different from each other,thereby approximating or otherwise mimicking the regression vector ofthe characteristic in entirely different ways. In other embodiments,however, one or both of the first and second ICE 302, 304 may beentirely or substantially disassociated with the characteristic ofinterest.

Briefly, manufacturing an ICE can be a very complex and intricateprocess. In addition, when an ICE is manufactured specifically to mimicthe regression vector of a characteristic of interest, this process canbecome even more complicated. As a result, it is common to producenon-predictive or poorly made ICE that, when tested, fail to accuratelyor even remotely be associated with the characteristic of interest(e.g., a disassociated ICE). In some cases, these non-predictive ICE mayreturn an arbitrary regression vector when tested or otherwise exhibitan arbitrary transmission function. In other cases, the non-predictiveICE may be considered “substantially” disassociated with thecharacteristic of interest in that the ICE only slightly mimics theregression vector of the characteristic but is nonetheless considerednon-predictive. In yet other cases, the non-predictive ICE may return aregression vector that closely mimics another characteristic of thesubstance being tested, but not the characteristic of interest.

Additional information and advantages of using multiple associated ordisassociated ICE in optical computing devices to determine a singlecharacteristic of interest is further described in co-pending U.S.patent application Ser. Nos. XX/XXX,XXX (atty. docket no.2012-IP-055117U1) and XX/XXX,XXX (atty. docket no. 2012-IP-055117U2),filed herewith concurrently, the contents of which are herebyincorporated by reference in their entireties.

As shown in FIG. 3 a, the optically interacted radiation 206 is directedto the optical computing device 300 and the beam splitter 208 againseparates the optically interacted radiation 206 into first and secondbeams of light 206 a,b. The first beam of light 206 a is directed intothe first or primary channel A1 and conveyed to the first ICE 302 whichgenerates a first modified electromagnetic radiation 306 correspondingto the characteristic or analyte of interest of the sample 202. Thefirst detector 212 may be arranged to receive the first modifiedelectromagnetic radiation 306 from the first ICE 302 and quantify theresulting signal in the form of a first output signal 310.

As illustrated, the second ICE 304 is arranged within what wouldnormally be used as a reference channel configured to normalize thefirst output signal 310 derived from the primary channel A1 in view ofradiating deviations of the electromagnetic radiation source 201.Arranging the second ICE 304 in the typical reference channel, however,now provides a new type of reference channel A2 and, similar to theprimary channel A1, the reference channel A2 is also configured toprovide an output corresponding to the characteristic or analyte ofinterest of the sample 202. Consequently, the reference channel A2 mayalso be considered, in at least some cases, as a type of primary channelof the device 300, substantially similar to the first primary channelA1. As will discussed below, embodiments are contemplated herein whichinclude several primary “A” channels in a single optical computingdevice, where each primary “A” channel is configured to provide anoutput corresponding to the characteristic or analyte of interest of thesample 202.

In FIG. 3 a, the second beam of light 206 b is directed into thereference channel A2 and conveyed to the second ICE 304 which generatesa second modified electromagnetic radiation 308 corresponding to thecharacteristic or analyte of interest of the sample 202. The seconddetector 216 may be arranged to receive the second modifiedelectromagnetic radiation 308 from the second ICE 304 and quantify theresulting signal in the form of a second output signal 312. Thecorresponding voltages returned from each detector 212, 216 areindicative of the dot product of the optical interaction of the firstbeam of light 206 a with the first ICE 302 and the optical interactionof the second beam of light 206 b with the second ICE 304, respectively,as a function of the concentration of the characteristic of interest ofthe sample 202.

In some embodiments, the first ICE 302 may be configured to bepositively correlated and the second ICE 304 may be configured to benegatively correlated. In other words, the voltage of the output signal310 in the primary channel A1 may tend to increase as the concentrationof the characteristic of interest increases, and the voltage of theoutput signal 318 in the reference channel A2 may tend to decrease asthe concentration of the characteristic of interest increases. In otherembodiments, however, the first ICE 302 may be configured to benegatively correlated and the second ICE 304 may be configured to bepositively correlated. In yet other embodiments, each of the first andsecond ICE 302, 304 may be positively correlated or negativelycorrelated, without departing from the scope of the disclosure.

As illustrated, the optical computing device 300 may further include athird detector 314, according to one or more embodiments. The thirddetector 314 may be substantially similar to the first and seconddetectors 212, 216 and may be used in the device 300 to detect radiatingdeviations stemming from the electromagnetic radiation source 201.Accordingly, a second or true reference channel B may be included in thedevice 300 and may serve the same purpose as the reference channel Bdescribed above with reference to FIGS. 2 a and 2 b. As illustrated, abeam splitter 316 may be arranged to reflect a portion of the opticallyinteracted light 206 toward the third detector 314 in order to generatea compensating signal 318 generally indicative of radiating deviations.The compensating signal 318 may be substantially similar to thecompensating signal 218 discussed above with reference to FIGS. 2 a and2 b, and therefore will not be described again in detail. In otherembodiments, however, the third detector 314 may be arranged so as toreceive electromagnetic radiation 204 directly from the electromagneticsource 201, as described in more detail below. In yet other embodiments,the third detector 314 may be arranged so as to receive electromagneticradiation reflected off of either of the ICE 302, 304 and likewisegenerate the compensating signal 318.

The first and second output signals 310, 312 may then be received by andcomputationally combined in the signal processor 220 to determine thecharacteristic of interest in the sample 202. In one or moreembodiments, computationally combining the first and second outputsignals 310, 312 is desired. This computation may involve a variety ofmathematical relationships, including, for example, a linearrelationship, a polynomial function, an exponential function, and or alogarithmic function, or a combination thereof. In these cases, avariety of normalization mathematics between the output signals 310, 312and the compensating signal 318 may be applied in order to take intoaccount any radiating deviations detected by the third detector 314. Forexample, the output signals 310, 312 may each be normalized by dividingeach by the compensating signal 318 to achieve, for example, A1/B andA2/B, before the mathematical relationship between A1/B and A2/B isapplied. In other cases, the mathematical relationship between A1 and A2may be applied, with the resultant subsequently normalized by channel B.In even other cases, a combination of these two normalization methodsmay be applied. Those skilled in the art will be familiar with bothgeneral methods, and can choose which method is most applicable giventhe specific relationships involved. Finally, it is understood by thoseskilled in the art that fractions or multiples of the quantity B may beemployed, as well as multiplication of the quantity (1/B).

Referring now to FIG. 3 b, illustrated is another exemplary opticalcomputing device 320, according to one or more embodiments. The device320 may be substantially similar to the device 300 described above withreference to FIG. 3 a and therefore may be best understood withreference thereto, where like numerals represent like elements notdescribed again in detail. In FIG. 3 b, the optically interactedradiation 206 is again directed into the first or primary channel A1 andconveyed to the first ICE 302 which generates a first modifiedelectromagnetic radiation 306 corresponding to the characteristic oranalyte of interest of the sample 202. The first detector 212 receivesthe first modified electromagnetic radiation 306 from the first ICE 302and provides the first output signal 310.

The second ICE 304 may again be arranged within what could normally beused as a reference channel for the device 320 and otherwise used tonormalize the first output signal 310 derived from the primary channelA1 in view of radiating deviations of the electromagnetic radiationsource 201. Specifically, the second ICE 304 is arranged in newreference channel A2 and, similar to the primary channel A1, may beconfigured to provide an output corresponding to the characteristic oranalyte of interest of the sample 202. As depicted, the second ICE 304may be configured to optically interact with a portion of theelectromagnetic radiation 204 directly radiated by the electromagneticradiation source 201. In one or more embodiments, for example, a beamsplitter 322 may be configured to split the electromagnetic radiation204 and direct a portion thereof in the reference channel A2 toward thesecond ICE 304. In other embodiments, however, the second ICE 304 may bearranged within the reference channel A2 so as to receive theelectromagnetic radiation 204 directly from the electromagneticradiation source 201, instead of receiving a reflected portion thereof.Those skilled in the art will readily recognize that the referencechannel A2 may be defined in a variety of locations within the opticalcomputing device 320, or any of the devices described herein, withoutdeparting from the scope of the disclosure.

The second ICE 304 generates the second modified electromagneticradiation 308 and conveys the same to the second detector 216. Thesecond detector 216 may be configured to receive and quantify the secondelectromagnetic radiation 308 and provide the second output signal 312which may be directed toward the signal processor 220.

As illustrated, the optical computing device 320 may further include thethird detector 314 used to detect radiating deviations stemming from theelectromagnetic radiation source 201. In one embodiment, the thirddetector 314 may be arranged to receive a portion of the opticallyinteracted light 206 as reflected from the beam splitter 316. In otherembodiments, however, the third detector 314 may be arranged to receivea portion of the electromagnetic radiation 204 as reflected from anotherbeam splitter 324 arranged within the reflected portion of theelectromagnetic radiation 204 as derived from the first beam splitter322. Accordingly, a true reference channel B may also be included in thedevice 300 and may serve the same purpose as the reference channel Bdescribed above with reference to FIGS. 2 a and 2 b. As illustrated, abeam splitter 316 may be arranged to reflect a portion of the opticallyinteracted light 206 toward the third detector 314 in order to generatea compensating signal 318 generally indicative of radiating deviations,as generally described above.

The compensating signal 318 in the second reference channel B may bedirected to the signal processor 220 and computationally combined withthe first and second output signals 310, 312 derived from the primaryand first reference channels A1, A2, respectively, in order tocompensate for any electromagnetic radiating deviations stemming fromthe electromagnetic radiation source 201. As discussed above, the ratioof the light intensity derived from the primary and first referencechannels A1, A2 may be divided by the light intensity derived from thesecond reference channel B, and the resulting output is related to theanalyte concentration or characteristic of interest. In one embodiment,for example, the compensating signal 318 and the first and second outputsignals 310, 312 are combined using principal component analysistechniques such as, but not limited to, standard partial least squareswhich are available in most statistical analysis software packages(e.g., XL Stat for MICROSOFT® EXCEL®; the UNSCRAMBLER® from CAMOSoftware and MATLAB® from MATHWORKS®). In other embodiments, thecompensating signal 318 is used simply to inform the user of thecondition of the electromagnetic radiation source 201, e.g., whether thesource 201 is functioning properly.

As will be appreciated by those skilled in the art, more than two ICE302, 304 may be used in alternative configurations or embodiments,without departing from the scope of the disclosure. Moreover, it shouldbe noted that while FIGS. 3 a and 3 b show electromagnetic radiation asbeing transmitted through the first and second ICE 302, 304 in order togenerate the first and second modified electromagnetic radiations 306,308, respectively, it is also contemplated herein to reflect theelectromagnetic radiation off of the first and second ICE 302, 304 andequally generate the corresponding first and second modifiedelectromagnetic radiations 306, 308, without departing from the scope ofthe disclosure.

It has been discovered that usage of one or more ICE in both the primaryand reference channels A1, A2 may enhance the sensitivity and detectionlimits of the optical computing device 300 beyond what would otherwisebe attainable with a single ICE design that utilizes a dedicatedreference channel B for normalizing electromagnetic radiationfluctuations, such as is described above with reference to FIGS. 2 a and2 b. This was entirely unexpected and would be considered whollyunobvious to those skilled in the art. For instance, the typicalreference channel B in optical computing devices is a spectrally neutralchannel and therefore dedicated solely to providing a ratio denominatoruseful in normalizing the output signal derived from the primary channelA against radiating deviations. Placing an ICE in the reference channelB would be wholly unobvious since the ICE is designed to be spectrallyactive and therefore has a spectrum associated with it which opticallyinteracts with the second light beam 206 b and changes its spectralcharacteristics. Accordingly, with the second ICE 304 arranged in thereference channel A2, as depicted in FIG. 3 a, the reference channel isno longer used for its intended purpose but nonetheless has been foundto dramatically increase the sensitivities and detection limits of thedevice 300. These unexpected results are especially possible even in thepresence of various interferents.

As further explanation, methods of how to design and build single ICEelements with optimal performance characteristics are disclosed in U.S.Pat. No. 7,711,605 and U.S. Pat. Pub. No. 2010/0153048, incorporatedherein by reference to the extent not inconsistent with the presentdisclosure. Using the methods described therein, literally thousands andhundreds of thousands of individual unique designs are created andoptimized for performance, thereby exhausting the optimal solution spaceavailable and yielding the best solutions possible. Those skilled in theart will readily recognize that ICE designs can be particularlysensitive to small changes in their optical characteristics. Thus, anymodification of the optical characteristic (e.g., changes made to theparticular transmission function) with, for example, additional ICEcomponents, would be considered as degrading the performance of theoptical computing device, and in most cases, quite rapidly with onlysmall changes. And indeed, it has been discovered that spectralcomponents (i.e., ICE components or designs) arranged in the referencechannel B do degrade the overall performance in some instances.

However, it was unexpectedly discovered that some spectral components,including some preferred ICE designs, can substantially enhance overalldevice performance when arranged in the typical reference channel B. Itwas further discovered, that these enhancements are not minoradjustments or improvements, but can enhance performance involvingfactors and/or orders of magnitude of improvement. It was yet furtherdiscovered that performance enhancements can be obtained withoutsubstantial compromise or trade-off of other important characteristics.It was also discovered that the ICE arranged in the typical referencechannel B may or may not be configured to be associated with thecharacteristic of the sample 202. Finally, generic classes of ICEdesigns were discovered, and their preferred usage in the referencechannel B uncovered, as generally described herein.

Referring to FIG. 4 a, for example, illustrated is a graph 400indicating the detection of a particular characteristic of a sampleusing one ICE arranged in the primary channel A, and another ICE in thereference channel B. It will be appreciated that the graph 400 and thedata presented therein are merely used to facilitate a betterunderstanding of the present disclosure, and in no way should the theybe read to limit or define the scope of the invention. The graph 400indicates the detection of the methane gas to oil ratio (GOR) in tworadically different oils from concentrations from 0 to 1000 scuft/bbl(standard cubic feet per standard barrel) under various pressures andtemperatures associated with downhole oil field conditions. The two oilsare a black, high asphaltene content optically opaque oil sampleobtained from the Gulf of Mexico, and a light, low asphaltene,relatively transparent, high sulfur content oil sample obtained fromSaudi Arabia. The graph 400 depicts the accuracy (standard deviation) ofmeasuring the GOR for both oils across the entire 0 to 1000 scuft/bblconcentration range of interest for an optical computing device (e.g.,the optical device 300, or any of the exemplary optical computingdevices disclosed herein) on the X-axis.

Results are shown for five different individual ICE designs and with thevarious unique combinations of the five with one of the ICE designs inthe reference channel B. As shown, a single ICE design without an ICE inthe reference channel B (i.e., shown as triangles) can yield an accuracyranging between a predictive 19.2% of full scale (190 scuft/bbl) and anon-predictive 34.9% of full scale (349 scuft/bbl).

The sensitivity of the device (e.g., the optical devices 300 or 320, orany of the exemplary optical computing devices disclosed herein),another key performance attribute important to the detection limits, isalso shown in the graph on the Y axis. The units of sensitivity are theabsolute magnitude of the % change in detector signal output observedover the entire GOR concentration range (0 to 1000 scuft/bbl) ofinterest. Regarding sensitivity, the larger the magnitude of the %change, the more sensitive and desirable is the system as greatersensitivity can enable better detectability and performance limits,lower costs, and other important benefits. As shown, sensitivities forthe standard configuration involving a neutral reference channel B, butwithout an ICE arranged in the reference channel B (i.e., shown astriangles) range from 3.3% to 4.9%.

When an ICE design is arranged in the reference channel B, however, theperformance may be enhanced (i.e., shown as squares). For example, byplacing an ICE in the reference channel B, accuracies were improved froma non-predictive 34.9% (349 scuft/bbl) to a highly predictive 1.1% (11scuft/bbl), or about a factor of 17× improvement over the best singleICE with neutral reference case, and about a factor of 31× over thenon-predictive case. Sensitivities were also improved for manycombinations, obtaining a factor of between 1.5 to almost 3× of that ofa single ICE design without a spectral element (i.e., additional ICE) inthe reference channel.

It has been found that increases in sensitivity are generallyaccompanied by decreases in accuracy for single ICE solutions. Thus, onesingle ICE design may have superior sensitivity over another, but willgenerally be found to be less accurate. Accuracy and sensitivity, two ofthe most important performance parameters for optical computing devices,are therefore generally trade-offs. The improvement in accuracydiscovered by using an ICE in the reference channel B, as shown in FIG.4 a, was totally unexpected. Even more unexpected was the result thatboth the accuracy and sensitivity could be simultaneously increased orat least maintained. For example, three of the unique combinations withan ICE in the reference channel B show both a dramatic enhancement inaccuracy and an improvement of approximately 1.5 to 3× in sensitivity.Three showed a substantial improvement in sensitivity (and thereforelower detection limits) while maintaining about the same accuracy.

It should be noted that these unexpected results were not achieved forall combinations of ICE designs in the reference channel B. Instead,there were three combinations, in particular, where the accuracyimproved substantially but the sensitivity decreased. Moreover, onecombination was tested where the accuracy was not improved, but thesensitivity substantially decreased. However, the graph 400 clearlydemonstrates the ability to dramatically increase device performance byplacing a spectral component (e.g., an ICE design) in the referencechannel B as opposed to using the traditional non-spectral component.Moreover, the ICE arranged in the reference channel B could either beassociated (predictive) or substantially disassociated (non-predictive)with the characteristic of interest (GOR in this case).

Referring now to FIG. 4 b, with continued reference to FIG. 4 a,illustrated is a graph 410 showing the calibration plots for all fivedifferent ICE designs shown in the graph 400, without any spectralelements arranged in the corresponding reference channel B. Similar tothe graph 400 of FIG. 4 a, the graph 410 and the data presented thereinare merely used to facilitate a better understanding of the presentdisclosure, and in no way should the they be read to limit or define thescope of the invention. A calibration plot was obtained for each of thedifference ICE designs by adding various methane concentrations to theGulf of Mexico oil, and then plotting the resulting signal on the X-axisas a function of the GOR on the Y-Axis. As depicted in the graph 410,generally two different behaviors are observed. In the cases of ICE 1(412), ICE 3 (414) and ICE 4 (416), the slope of the curves arenegative, meaning that the resulting ICE signal derived from the primarychannel A was observed to decrease as the concentration of interest(i.e., GOR) increased. On the other hand, the slope of the respectivecurves for ICE 2 (418) and ICE 5 (420) are positive, meaning that theresulting ICE signal derived from the primary channel A was observed toincrease as the concentration of GOR increased. Accordingly, ICE 1(412), ICE 3 (414) and ICE 4 (416) may each be considered “negativelycorrelated,” and ICE 2 (418) and ICE 5 (420) may each be considered“positively correlated.”

To Applicant's knowledge, there has been no discussion of or particularimportance assigned to the positive or negative nature/correlation ofICE designs. Nonetheless, it was discovered that the sign of aparticular ICE design response, whether it be positively or negativelycorrelated, may be important, especially in embodiments usingcombinations of ICE designs and/or embodiments that use spectralelements, such as ICE, in the reference channel B.

This importance can be better appreciated with reference to thesensitivity vs. accuracy graph 430 depicted in FIG. 4 c. Again, as withgraphs 400 and 410 of FIGS. 4 a and 4 c, respectively, the graph 430 andthe data presented therein are merely used to facilitate a betterunderstanding of the present disclosure, and in no way should the theybe read to limit or define the scope of the invention. The graph 430re-plots the graph 400 from FIG. 4 a above, but categorizes the variousICE combinations by their positive and negative natures. As indicatedabove in the graph 410, of the five ICE designs tested, two werepositively correlated and three were negatively correlated. Asillustrated in the graph 430, when ICE components having the same signare placed in both the primary and reference channels (shown asdiamonds), the accuracy may increase but sensitivity may decrease ascompared to embodiments where there is only an ICE component placed inthe primary channel (shown as triangles). Moreover, in embodiments whereICE components having different signs are placed in the primary andreference channels (shown as squares), however, the accuracy andsensitivity may increase as compared to embodiments having same sign ICEcomponents placed in both the primary and reference channels (shown asdiamonds) and embodiments where there is only an ICE component placed inthe primary channel (shown as squares).

Accordingly, the graph 430 may first illustrate that benefits andperformance enhancements can be gained by placing a spectral element,such as an ICE component, in the reference (e.g., the “B” channel),shown as diamonds. Also, dramatic improvements in sensitivity wereobtained for all six combinations where the primary channel ICE (e.g.,the “A” channel ICE) and the reference channel ICE (e.g., the reference“B” channel ICE) were of the same sign, either both “positivelycorrelated” or both “negatively correlated.” The graph 430 may alsoillustrate that dramatic improvements in accuracy can be obtainedregardless of the signs of the ICE in the reference “B” channel. Forexample, substantial improvements can be obtained if the two ICE havesimilar signs or if they have dissimilar signs. Moreover, the graph 430may indicate that reductions in sensitivity were generally observed ifthe two ICE components had the same sign. For instance, two negativelycorrelated ICE designs or two positively correlated ICE designs cangenerally result in lower sensitivity when compared to a single ICEelement and no spectral element (i.e., no ICE component) in thereference channel. The best results, yielding both dramatically improvedaccuracies and sensitivities, were obtained when the ICE in thereference “B” channel had the opposite sign as that in the primary “A”channel, as shown as squares. It should be noted that performanceenhancements could also be obtained from ICE components that were eitherassociated, or disassociated with the characteristic of interest.

Referring to FIG. 4 d, illustrated is a table 440 that summarizes thetests of the five ICE depicted in the graph 430 of FIG. 4 c. Similar tothe graphs 400, 410, and 430, the table 440 and the data presentedtherein are merely used to facilitate a better understanding of thepresent disclosure, and in no way should the they be read to limit ordefine the scope of the invention. As shown in the table 440, improvedaccuracies and sensitivities were most-often obtained when the ICE inthe reference “B” channel had the opposite sign as that in the primary“A” channel. For example, the first ICE 1 was tested as negativelycorrelated and having a GOR accuracy of 30.7% of full range (307scft/bbl) and a full scale sensitivity of −4.9% which indicates that thesignal decreased 4.9% at the maximum concentration value (1000 GOR) fromits value at the minimum concentration (0 GOR). In contrast, the secondICE 2 was tested as positively correlated and having an accuracy of27.0% and a full scale sensitivity of +3.3%.

Accordingly, the discovery of using positively or negatively correlatedICE components, and their use either in combination and/or in thereference channel, has been shown, in at least some cases, to yieldimproved performance over single ICE systems or ICE systems withspectrally neutral reference channels. Those skilled in the art willfurther appreciate that various combinations, not just linearcombinations, and various and multiple primary “A” and reference “B”channels can also be employed or combined to potentially improve resultsover the single ICE design, or single ICE with no spectral element inthe reference channel embodiments.

Referring now to FIG. 5, illustrated is another exemplary opticalcomputing device 500, according to one or more embodiments. The device500 may be somewhat similar to the optical computing device 300described above with reference to FIG. 3 a, and therefore may be bestunderstood with reference to FIG. 3 a where like numerals indicate likeelements that will not be described again in detail. As illustrated, thedevice 500 may include a first ICE 502 and a second ICE 504. The firstand second ICE 502, 504 may be similar in construction to the ICE 100described above with reference to FIG. 1, and configured to be eitherassociated or disassociated with a particular characteristic of thesample. Moreover, the first and second ICE 502, 504 may be configured tobe either positively or negatively correlated. Embodiments arecontemplated herein that include one or more beam splitters, mirrors,and the like in order to allow the electromagnetic radiation 204 tooptically interact with both the sample 202 and first and second ICE502, 504, without departing from the scope of the disclosure. Indeed,one or more beam splitters, mirrors, and the like may be used inconjunction with any of the exemplary embodiments disclosed herein,without departing from the scope of the disclosure.

As illustrated, the first and second ICE 502, 504 may be coupledtogether to form a monolithic structure, but in other embodiments may beseparated or otherwise arranged in series without departing from thescope of the disclosure. Moreover, the first and second ICE 502, 504 maybe arranged to receive the optically interacted light 206, as depicted,but may equally be arranged antecedent to the sample 202 and thereforedirectly receive the electromagnetic radiation 204. In one embodiment,the first ICE 502 may be smaller than the second ICE 504 or otherwisearranged such that a portion of the optically interacted light 206passes through only the second ICE 504 and generates the first modifiedelectromagnetic radiation 306. Another portion of the opticallyinteracted light 206 may pass through a combination of both the firstand second ICE 502, 504 and thereby generate the second modifiedelectromagnetic radiation 308. As a result, the device 500 may provide afirst or primary channel A1 that incorporates the optically interactedlight 206 passing through the second ICE 504 and thereafter generatingthe first modified electromagnetic radiation 306, and a second orreference channel A2 that incorporates the optically interacted light206 passing through both the first and second ICE 502, 504 andthereafter generating the second modified electromagnetic radiation 308.

In at least one embodiment, the first ICE 502 may be configured to bepositively correlated and the second ICE 502 may be configured to benegatively correlated. In other embodiments, however, the first ICE 502may be configured to be negatively correlated and the second ICE 504 maybe configured to be positively correlated. In yet other embodiments,each of the first and second ICE 502, 504 may be positively correlatedor negatively correlated, without departing from the scope of thedisclosure.

The first and second modified electromagnetic radiations 306, 308 may bedirected to a detector 506, which may be a split or differentialdetector, having a first detector portion 506 a and a second detectorportion 506 b. In other embodiments, however, the detector 506 may be adetector array, as known in the art, without departing from the scope ofthe disclosure. In operation, the first detector portion 506 a formspart of the primary channel A1 and may be configured to receive thefirst modified electromagnetic radiation 306 and generate a first outputsignal 508 a. Furthermore, the second detector portion 506 b forms partof the reference channel A2 and may be configured to receive the secondmodified electromagnetic radiation 308 and generate a second outputsignal 508 b. In some embodiments, the detector 506 may be configured tocomputationally combine the first and second signals 508 a,b in order todetermine the characteristic of the sample, for example when using adifferential detector or quad-detector. In other embodiments, the firstand second signals 508 a,b may be transmitted to or otherwise receivedby the signal processor 220 communicably coupled to the detector 506 andconfigured to computationally combine the first and second outputsignals 508 a,b in order to determine the characteristic of the sample202. Again, computationally combining the first and second signals 508a,b may entail determining the ratio of the two signals, such that aratio of the primary channel A1 against the reference channel A2 isobtained. In some embodiments, the signal processor 220 may be acomputer including a non-transitory machine-readable medium, asgenerally described above.

In at least one embodiment, the device 500 may further include a seconddetector 510 that may function similarly to the third detector 314described above with reference to FIG. 3 a, and thereby further providea second or true reference channel B. In operation, the detector 510 maybe arranged to receive and detect optically interacted light 512 inorder to generate the compensating signal 318 generally indicative ofradiating deviations of the electromagnetic radiation source 201. Thecompensating signal 318 may be directed to the signal processor 220 andcomputationally combined with the first and second output signals 310,312 in order to compensate for any electromagnetic radiating deviationsstemming from the electromagnetic radiation source 201.

It should be noted that even though the electromagnetic radiation 204 isshown in FIG. 5 as optically interacting with the sample 202 beforereaching the first and second ICE 502, 504, the first and second ICE502, 504 nonetheless are considered to have optically interacted withthe electromagnetic radiation 204, albeit subsequent to the sample 202.In other embodiments, the electromagnetic radiation 204 may opticallyinteract with the first and second ICE 502, 504 before reaching thesample 202, and the sample 202 nonetheless is considered to haveoptically interacted with the electromagnetic radiation 204, albeitsubsequent to the first and second ICE 502, 504. Furthermore,embodiments are contemplated herein where the first ICE 502 is arrangedon one side of the sample 202, and the second ICE 504 is arranged on theopposite side of the sample 202. As a result, the electromagneticradiation 204 may optically interact with the first ICE 502 prior tooptically interacting with the sample 202, and subsequently opticallyinteracting with the second ICE 504. It will be appreciated that any andall of the embodiments disclosed herein may include any of the exemplaryvariations discussed herein, such as arranging the sample 202 before orafter the first and second ICE 502, 504, or arranging the ICE 502, 504in linear or non-linear configurations.

Referring now to FIG. 6, with continued reference to FIG. 5, illustratedis another optical computing device 600, according to one or moreembodiments. The device 600 may be somewhat similar to the opticalcomputing device 500 described with reference to FIG. 5, therefore thedevice 600 may be best understood with reference thereto, where likenumerals indicate like elements. The device 600 may include a first ICE602 and a second ICE 604 similar in construction to the ICE 100described above with reference to FIG. 1, and configured to be eitherassociated or disassociated with a particular characteristic of thesample 202, such as is described above with reference to the first andsecond ICE 302, 304 of FIG. 3 a. Moreover, in at least one embodiment,the first ICE 602 may be configured to be positively correlated and thesecond ICE 602 may be configured to be negatively correlated. In otherembodiments, however, the first ICE 602 may be configured to benegatively correlated and the second ICE 604 may be configured to bepositively correlated. In yet other embodiments, each of the first andsecond ICE 602, 604 may be positively correlated or negativelycorrelated, without departing from the scope of the disclosure.

As illustrated, the first and second ICE 602, 604 may be arrangedgenerally parallel relative to one another and configured to receive theoptically interacted light 206. As with prior embodiments, however, thefirst and second ICE 602, 604 may equally be arranged antecedent to thesample 202, without departing from the scope of the disclosure. Inoperation, the first ICE 602 may receive a portion of the opticallyinteracted light 206 and thereby generate the first modifiedelectromagnetic radiation 306. The second ICE 604 may be configured toreceive another portion of the optically interacted light 206 andthereby generate the second modified electromagnetic radiation 308. As aresult, the device 600 may provide a first or primary channel A1 thatincorporates the optically interacted light 206 passing through thefirst ICE 602 and thereafter generating the first modifiedelectromagnetic radiation 306, and a second or reference channel A2 thatincorporates the optically interacted light 206 passing through thesecond ICE 604 and thereafter generating the second modifiedelectromagnetic radiation 308.

The first and second modified electromagnetic radiations 306, 308 may bedirected to the detector 506 to generate the first output signal 508 ain the primary channel A1 and the second output signal 508 b in thereference channel A2 as corresponding to the first and second modifiedelectromagnetic radiations 306, 308, respectively. Specifically, thefirst detector portion 506 a may be configured to receive the firstmodified electromagnetic radiation 306 and generate the first outputsignal 508 a, and the second detector portion 506 b may be configured toreceive the second modified electromagnetic radiation 308 and generatethe second output signal 508 b. In some embodiments, the detector 506may be configured to computationally combine the first and second outputsignals 508a,b in order to determine the characteristic of the sample.In other embodiments, however, the first and second signals 508 a,b maybe received by a signal processor 220 communicably coupled to thedetector 506 and configured to computationally combine the first andsecond signals 508 a,b in order to determine the characteristic of thesample.

In some embodiments, the detector 506 is a single detector butconfigured to time multiplex the first and second modifiedelectromagnetic radiations 306, 308. For example, the first ICE 602 maybe configured to direct the first modified electromagnetic radiation 306toward the detector 506 at a first time T1, and the second ICE 604 maybe configured to direct the second modified electromagnetic radiation308 toward the detector 506 at a second time T2, where the first andsecond times T1, T2 are distinct time periods that do not spatiallyoverlap. Consequently, the detector 506 receives at least two distinctbeams of modified electromagnetic radiation 306, 308 which may becomputationally combined by the detector 506 in order to provide anoutput in the form of a voltage that corresponds to the characteristicof the sample.

In one or more embodiments, in order to provide the first and secondtimes T1, T2, the device 600 may include more than one electromagneticradiation source 201. In other embodiments, the electromagneticradiation source 201 may be pulsed in order to provide the first andsecond times T1, T2. In yet other embodiments, each ICE 602, 604 may bemechanically positioned to interact with the electromagnetic radiationbeam at two distinct times. In yet other embodiments, theelectromagnetic radiation beam may be deflected, radiated, re-radiated,or diffracted to interact with the two different ICE elements at timesT1 and T2. Moreover, it will be appreciated that more than the first andsecond ICE 602, 604 may be used, thereby generating additional primarychannels (e.g., A3, A4, . . . An), and the detector 506 may therefore beconfigured to time multiplex each additional beam of opticallyinteracted light to provide the cumulative voltage corresponding to thecharacteristic of the sample.

In at least one embodiment, the device 600 may further include thesecond detector 510 that may function similarly to the third detector314 described above with reference to FIG. 3 a, and thereby furtherprovide a second or true reference channel B. As illustrated, a beamsplitter 606 may be arranged to reflect a portion of the opticallyinteracted light 206 toward the second detector 510 in order to generatea compensating signal 318 generally indicative of radiating deviationsof the electromagnetic radiation source 201. In other embodiments,however, the second detector 510 may be arranged so as to receiveelectromagnetic radiation 204 directly from the electromagnetic source201 or electromagnetic radiation reflected off of either of the ICE 302,304 and likewise generate the compensating signal 318. The compensatingsignal 318 may be directed to the signal processor 220 andcomputationally combined with the first and second output signals 310,312 in order to compensate for any electromagnetic radiating deviationsstemming from the electromagnetic radiation source 201. As a result, asecond reference channel B may be included in the device 300 andemployed substantially similarly to the reference channel B describedabove with reference to FIGS. 2 a and 2 b. In other embodiments, thecompensating signal 318 may be used to inform the user of the conditionof the electromagnetic radiation source 201, e.g., whether the source201 is functioning properly.

Referring now to FIG. 7, illustrated is another optical computing device700, according to one or more embodiments. The device 700 may besomewhat similar to the optical computing devices 500, 600 describedwith reference to FIGS. 5 and 6 and therefore the device 700 may be bestunderstood with reference thereto, where like numerals indicate likeelements. The device 700 may include at least two ICE, including a firstICE 702 a and a second ICE 702 b, but may further include one or moreadditional ICE 702 n. Each ICE 702 a-n may be similar in construction tothe ICE 100 described above with reference to FIG. 1, and configured tobe either associated or disassociated with a particular characteristicof the sample 202, such as is described above with reference to thefirst and second ICE 302, 304 of FIG. 3 a. Moreover, each ICE 702 a-nmay be configured to be either positively or negatively correlated,including various combinations thereof.

The device 700 may further include a plurality of detectors, such as afirst detector 704 a, a second detector 704 b, and one or moreadditional detectors 704 n. The first, second, and additional ICE 702a-n may each be arranged in series relative to one another andconfigured to optically interact with the electromagnetic radiation 204either through the sample 202 or through varying configurations ofreflection and/or transmission between adjacent ICE 702 a-n. In theembodiment specifically depicted, the first ICE 702 a may be arranged ina first primary channel A1 to receive the optically interacted radiation206 from the sample 202. As with prior embodiments, however, the firstICE 702 a may equally be arranged antecedent to the sample 202, andtherefore optically interact with the electromagnetic radiation 204. Thefirst ICE 702 a may be configured to transmit a modified electromagneticradiation 706 a to the first detector 704 a and simultaneously conveyvia reflection optically interacted light 708 toward the second ICE 702b. The second ICE 702 b may be arranged in a second primary channel A2and configured to convey a second optically interacted light 706 b viareflection toward the second detector 704 b, and simultaneously transmitadditional optically interacted light 710 toward the additional ICE 702n.

The additional ICE 702 n may be arranged within a reference channel A3,which would otherwise be used to detect radiating deviations of theelectromagnetic radiation source 201, but now is used to help determinethe characteristic of the sample 202. Accordingly, the reference channelA3 may function substantially similarly to one of the primary channelsA1, A2. In operation, the additional ICE 702 n may be configured toconvey an additional modified electromagnetic radiation 706 n viareflection toward the additional detector 704 n.

Those skilled in the art will readily recognize numerous alternativeconfigurations of the first, second, and additional ICE 702 a-n andcorresponding first and second primary channels A1, A2 and the referencechannel A3, without departing from the scope of the disclosure. Forexample, reflection of optically interacted light from a particular ICEmay be replaced with transmission of optically interacted light, oralternatively configurations may include the use of mirrors or beamsplitters configured to direct the electromagnetic radiation 204 (oroptically interacted radiation 206) to each of the first, second, andadditional ICE 702 a-n.

In at least one embodiment, the device 700 may further include thesecond detector 510 that may function similarly to the third detector314 described above with reference to FIG. 3 a, and thereby furtherprovide a second or true reference channel B. As illustrated, thedetector 510 receives and detects optically interacted light transmittedthrough the additional ICE 702 n and subsequently outputs thecompensating signal 318 indicative of electromagnetic radiatingdeviations. In at least one embodiment, the second detector 510 may becommunicably coupled to the signal processor 220 such that thecompensating signal 318 may be provided or otherwise conveyed thereto.

The first, second, and additional detectors 704 a-n may be configured todetect the first, second, and additional modified electromagneticradiation 706 a-n, respectively, within the corresponding first andsecond primary channels A1, A2 and the reference channel A3 and therebygenerate a first output signal 508 a, a second output signal 508 b, andone or more additional output signals 508 n, respectively. In someembodiments, the first, second, and additional output signals 508 a-nmay be received by the signal processor 220 communicably coupled to eachdetector 704 a-n and configured to computationally combine the first,second, and additional signals 508 a-n in order to determine thecharacteristic of the sample 202.

This computation may involve a variety of mathematical relationships,including, for example, a linear relationship, a polynomial function, anexponential function, and/or a logarithmic function, or a combinationthereof. In these cases, a variety of normalization mathematics betweenthe output signals 508 a, 508 b . . . 508 n and the compensating signal318 may be applied. For example, the output signals 508 a, 508 b . . .508 n may each be normalized by dividing them each by the compensatingsignal 318 to achieve, for example, A1/B, A2/B . . . A3/B, before themathematical relationship between A1/B and A2/B is applied. In othercases, the mathematical relationship between A1 and A2 may be applied,with the result normalized by B. In even other cases, a combination ofthese two normalization methods may be applied. Those skilled in the artwill be familiar with both general methods, and can choose which methodis most applicable given the specific relationships involved. In oneembodiment, for example, the compensating signal 318 and the outputsignals 508 a, 508 b, . . . 508 n are combined using principal componentanalysis techniques such as, but not limited to, standard partial leastsquares which are available in most statistical analysis softwarepackages (e.g., XL Stat for MICROSOFT® EXCEL®; the UNSCRAMBLER® fromCAMO Software and MATLAB® from MATHWORKS®). Finally, it is understood bythose skilled in the art that fractions or multiples of the quantity Bmay be employed, as well as multiplication of the quantity (1/B).

As will be appreciated, any number of ICE may be arranged within anynumber of primary channels or otherwise used in series in order todetermine the characteristic of the sample 202. In some embodiments,each of the first, second, and additional ICE 702 a-n may bespecially-designed to detect the particular characteristic of interestor otherwise be configured to be associated therewith. In otherembodiments, however, one or more of the first, second, and additionalICE 702 a-n may be configured to be disassociated with the particularcharacteristic of interest, and/or otherwise may be associated with anentirely different characteristic of the sample 202. In yet otherembodiments, each of the first, second, and additional ICE 702 a-n maybe configured to be disassociated with the particular characteristic ofinterest, and otherwise may be associated with an entirely differentcharacteristic of the sample 202.

Referring now to FIG. 8, illustrated is an alternative configuration ofthe optical computing device 700, according to one or more embodiments.In FIG. 8, a series of beam splitters 711 a, 711 b, 711 n may be addedto the first and second primary channels A1, A2 and the referencechannel A3, respectively, and used to separate or otherwise redirect theoptically interacted radiation 206 As depicted, each beam splitter 711a-n may be configured to produce and direct a respective beam 712 a, 712b, 712 n of optically interacted radiation 206 toward a correspondingICE 702 a-n. Each ICE 702 a-n may then be configured to transmit itsrespective modified electromagnetic radiation 706 a-n toward acorresponding detector 704 a-n, thereby generating the first, second,and additional output signals 508 a-n, respectively. The first, second,and additional signals 508 a-n may then be received by a signalprocessor 220 communicably coupled to each detector 704 a-n andconfigured to computationally combine the first, second, and additionalsignals 508 a-n in order to determine the characteristic of the sample202.

In some embodiments, the second detector 510 may again be used in thesecond or true reference channel B to detect electromagnetic radiatingdeviations exhibited by the electromagnetic radiation source 201, andthereby normalize the signals 508 a-n produced by the detectors 704 a-n.The second detector 510 may be communicably coupled to the signalprocessor 220 such that the compensating signal 318 indicative ofelectromagnetic radiating deviations may be provided or otherwiseconveyed thereto. The signal processor 220 may then be configured tocomputationally combine the compensating signal 318 with the signals 508a-n, and thereby normalize the signals 508 a-n and provide a moreaccurate determination of the characteristic of the sample.

Referring now to FIG. 9, illustrated is yet another alternativeconfiguration of the optical computing device 700, according to one ormore embodiments. As illustrated in FIG. 9, the optically interactedradiation 206 may be fed into or otherwise provided to, for example, anoptical light pipe 714. The optical light pipe 714 may be configured toconvey the optically interacted radiation 206 individually to each ofthe first and second primary channels A1, A2 and the reference channelA3. In some embodiments, the optical light pipe 714 may be a fiber opticbundle having a plurality of corresponding conveying bundles. Inoperation, a first bundle 714 a may be configured to convey opticallyinteracted radiation 206 to the first ICE 702 a in the first primarychannel A1 in order to generate the modified electromagnetic radiation706 a; a second bundle 714 b may be configured to convey opticallyinteracted radiation 206 to the second ICE 702 b in the second primarychannel A2 in order to generate the second optically interacted light706 b; and an additional bundle 714 n may be configured to conveyoptically interacted radiation 206 to the additional ICE 702 n in thereference channel A3 in order to generate the additional modifiedelectromagnetic radiation 706 n. At least one additional bundle 714 xmay be configured to convey optically interacted radiation 206 to thesecond detector 510 in the second or true reference channel B in orderto generate the compensating signal 318. Processing of the resultingmodified electromagnetic radiation 706 a-n and signals 508 a-n may beaccomplished as generally described above.

It should be noted that the use of optical light pipes, such as theoptical light pipe 714 discussed above, may be employed in any of thevarious embodiments and combinations discussed herein, without departingfrom the scope of the disclosure. Use of a light pipe, or a variationthereof, may prove advantageous in that the light pipe substantiallyremoves interferent obstruction that may otherwise contaminate theoptically interacted radiation 206 provided to the various ICEs.

Referring now to FIG. 10, illustrated is another optical computingdevice 1000, according to one or more embodiments. The device 1000 maybe somewhat similar to the optical computing devices 300 and 320described with reference to FIGS. 3 a and 3 b and therefore the device1000 may be best understood with reference thereto, where like numeralsindicate like elements. The device 1000 may include a movable assembly1002 having at least two ICEs associated therewith and variouscorresponding primary channels and at least one reference channel. Asillustrated, the movable assembly 1002 may be characterized at least inone embodiment as a rotating disc 1003, wherein the at least two ICEsare radially disposed for rotation therewith. Alternatively, the movableassembly 1002 may be characterized as a linear array 1005, wherein theat least two ICEs are laterally offset from each other. FIG. 10illustrates corresponding side and frontal views of both the rotatingdisc 1003 and the linear array 1005, each of which is described in moredetail below.

Those skilled in the art will readily recognize, however, that themovable assembly 1002 may be characterized as any type of movableassembly configured to sequentially align at least one detector withoptically interacted light 206 and/or one or more ICE. For example, themovable assembly 1002 may include such apparatus or devices as, but notlimited to, an oscillating or translating linear array of ICE, one ormore scanners, one or more beam deflectors, combinations thereof, or thelike. In other embodiments, the movable assembly 1002 may becharacterized as an assembly including a plurality of optical lightpipes (e.g., fiber optics) configured to perform optical beam splittingto a fixed array of ICE and/or detectors.

Varying embodiments of the rotating disc 1003 may include any number ofICE arranged about or near the periphery of the rotating disc 1003 andcircumferentially-spaced from each other. In the illustrated embodiment,the rotating disc 1003 includes a first ICE 1004 a, a second ICE 1004 b,a third ICE 1004 c, and a fourth ICE 1004 d, but it will be appreciatedthat the rotating disc 1003 may also include any number of additionalICE 1004 n as needed for the particular application. Each ICE 1004 a-nmay be similar in construction to the ICE 100 described above withreference to FIG. 1, and configured to be either associated ordisassociated with a particular characteristic of the sample 202, suchas is described above with reference to the first and second ICE 302,304 of FIG. 3 a. Moreover, each ICE 1004 a-n may be configured to beeither positively or negatively correlated, including variouscombinations thereof. In various embodiments, the rotating disc 1003 maybe rotated at a frequency of about 0.1 RPM to about 30,000 RPM.

In operation, the rotating disc 1003 may rotate such that eachindividual ICE 1004 a-n may be exposed to or otherwise opticallyinteract with the optically interacted radiation 206 for a distinctbrief period of time. In at least one embodiment, however, the movableassembly 1002 may be arranged antecedent to the sample 202 such thateach ICE 1004 a-n may be exposed to or otherwise optically interact withthe electromagnetic radiation 204 for a brief period of time. Uponoptically interacting with the optically interacted radiation 206 eachICE 1004 a-n may be configured to produce modified electromagneticradiation, for example, a first modified electromagnetic radiation 1006a emanating from the first ICE 1004 a, a second modified electromagneticradiation 1006 b emanating from the second ICE 1004 b, a third modifiedelectromagnetic radiation 1006 c emanating from the third ICE 1004 c, afourth modified electromagnetic radiation 1006 d emanating from thefourth ICE 1004 d, and additional modified electromagnetic radiation1006 n emanating from the one or more additional ICE 1004 n.

As each individual ICE 1004 a-n aligns with the optically interactedlight 206 to produce the modified electromagnetic radiations 1106 a-n,respectively, corresponding first, second, third, and fourth primarychannels A1, A2, A3, and A4 and one or more reference channels B arethereby generated. Since the device 1000 is not necessarily limited toany specific number of ICE 1004 a-n, a corresponding number of primarychannels may also be defined by the device 1000 (e.g., primarychannel(s) An). Moreover, it will be appreciated that, while therotating disc 1003 may include any number of additional ICE 1004 n asneeded, any number of corresponding or otherwise unrelated referencechannels B may also be included in the device 1000 (e.g., referencechannels B1, B2 . . . Bn), without departing from the scope of thedisclosure. Whereas at least one of the one or more reference channels Bwould otherwise be configured to detect radiating deviations of theelectromagnetic radiation source 201, embodiments are contemplatedherein where a spectrally active additional ICE 1004 n is arrangedwithin said reference channel B. As a result, the reference channel Bmay serve substantially the same purpose as the first, second, third,and fourth primary channels A1, A2, A3, A4 by detecting and determiningthe characteristic of the sample 202.

In one or more embodiments, however, at least one of the one or morereference channels B (e.g., B1, B2, . . . Bn) may include a neutralspectral element (not shown) configured to simply pass the opticallyinteracted radiation 206 without optical-interaction. As a result, theneutral element may be configured to provide a neutral signal to thedetector 212 that may be substantially similar to the compensatingsignal 318 as described above with reference to FIG. 3 a, and therebygenerate a true reference channel B, as generally described herein. Inoperation, the detector 212 may detect the neutral signal which may beindicative of radiating deviations stemming from the electromagneticradiation source 201.

Each beam of modified electromagnetic radiation 1006 a-n may be detectedby the detector 212 which may be configured to time multiplex themodified electromagnetic radiation 1006 a-n between theindividually-detected beams. For example, the first ICE 1004 a may beconfigured to direct the first modified electromagnetic radiation 1006 atoward the detector 212 at a first time T1, the second ICE 1004 b may beconfigured to direct the second modified electromagnetic radiation 1006b toward the detector 212 at a second time T2, and so on until the oneor more additional ICE 1004 n may be configured to direct the additionalmodified electromagnetic radiation 1006 toward the detector 212 at anadditional time Tn. Consequently, the detector 212 receives a pluralityof distinct beams of modified electromagnetic radiation 1006 a-n whichmay be computationally combined by the detector 212 in order to providean output in the form of a voltage that corresponds to thecharacteristic of the sample. In some embodiments, these beams ofmodified electromagnetic radiation 1006 a-n may be averaged over anappropriate time domain (e.g., about 1 millisecond to about 1 hour) tomore accurately determine the characteristic of the sample 202.

The time multiplexed computation from the various primary channels A1,A2, . . . An and reference channel(s) B (e.g., B1, B2, . . . Bn) mayinvolve a variety of mathematical relationships, including, for example,a linear relationship, a polynomial function, an exponential function,and or a logarithmic function, or a combination thereof. In these cases,a variety of normalization mathematics between the primary channels A1,A2, . . . An and reference channel(s) B may be applied. For example, thesignals A1, A2, . . . An may each be normalized by dividing them each byB1, B2, . . . Bn (or a mathematical combination of B1, B2, . . . Bn) toachieve, for example, A1/B, A2/B . . . An/B, before the mathematicalrelationship between A1/B and A2/B is applied. In other cases, themathematical relationship between A1, A2, . . . An may be applied, withthe resultant normalized by B1, B2 . . . Bn (or a mathematicalcombination of B1, B2 . . . Bn). In even other cases, a combination ofthese two normalization methods may be applied. Those skilled in the artwill be familiar with both general methods, and can choose which methodis most applicable given the specific relationships involved. In oneembodiment, for example, the compensating signal B1, B2 . . . Bn and theoutput signals A1, A2 . . . An are combined using principal componentanalysis techniques such as, but not limited to, standard partial leastsquares which are available in most statistical analysis softwarepackages (e.g., XL Stat for MICROSOFT® EXCEL®; the UNSCRAMBLER® fromCAMO Software and MATLAB® from MATHWORKS®). Finally, it is understood bythose skilled in the art that fractions or multiples of the quantity Bmay be employed, as well as multiplication of the quantity (1/B).

As will be appreciated, each of the ICE 1004 a-n may bespecially-designed to detect or otherwise configured to be associatedwith the particular characteristic of interest. In other embodiments,however, one or more of the ICE 1004 a-n may be configured to bedisassociated with the particular characteristic of interest, andotherwise may be associated with an entirely different characteristic ofthe sample 202. In yet other embodiments, each of the one or more ICE1004 a-n may be configured to be disassociated with the particularcharacteristic of interest, and otherwise may be associated with anentirely different characteristic of the sample 202. Advantages of thisapproach can include the ability to analyze multiple analytes inmultiple respective channels using a single optical computing device andthe opportunity to assay additional analytes simply by adding additionalICEs to the rotating disc 1003.

The linear array 1005 may also include the first, second, third, andfourth ICE 1004 a-d and the one or more additional ICE 1004 n, althoughaligned linearly as opposed to radially positioned. The linear array1005 may be configured to oscillate or otherwise translate laterally orvertically such that each ICE 1004 a-n is exposed to or otherwise ableto optically interact with the optically interacted radiation 206 for adistinct brief period of time. Similar to the rotating disc 1003, thelinear array 1005 may be configured to produce modified electromagneticradiation 1006 a-n. Again, as each individual ICE 1004 a-n aligns withthe optically interacted light 206 to produce the modifiedelectromagnetic radiations 1106 a-n, respectively, corresponding first,second, third, and fourth primary channels A1, A2, A3, and A4 and one ormore reference channels B (e.g., B1, B2, . . . Bn) are therebygenerated. As will be appreciated, any number of ICE 1004 a-n may bearranged on the linear array 1005 in order to determine thecharacteristic of the sample 202, and therefore any number ofcorresponding primary channels A1-A4 and additional reference channels Balso may be generated.

Moreover, as with the rotating disc 1003 embodiment, the detector 212may be configured to time multiplex the modified electromagneticradiation 1006 a-n between the individually-detected beams andsubsequently provide an output in the form of a voltage that correspondsto the characteristic of the sample 202. Even further, at least one ofthe ICE 1004 a-n may be a neutral element configured to provide aneutral signal to the detector 212 in a true reference channel B thatmay be computationally combined with the remaining beams of modifiedelectromagnetic radiation 1006 a-n to compensate for electromagneticradiating deviations stemming from the electromagnetic radiation source201.

Referring now to FIG. 11, with continued reference to FIG. 10,illustrated is another exemplary optical computing device 1100,according to one or more embodiments. The device 1100 may be somewhatsimilar to the device 1000 of FIG. 10, and therefore may be bestunderstood with reference thereto where like numerals indicate likeelements. The device 1100 may include a movable assembly 1102 similar insome respects to the movable assembly 1002 of FIG. 10. For example, FIG.11 illustrates an alternative embodiment of a rotating disc 1103. Therotating disc 1103 in FIG. 11, however, may include multipleradially-offset rows or arrays of ICE, such as a first radial array 1104a, a second radial array 1104 b, and one or more additional radialarrays 1104 n. Accordingly, while three radial arrays 1104 a, 1104 b,and 1104 n are shown in FIG. 11, it will be appreciated that therotating disc 1103 may include more or less than three arrays 1104 a-n,without departing from the scope of the disclosure.

Each radially-offset radial array 1104 a-n may include a plurality ofICE 1106 circumferentially-spaced from each other. Again, while aparticular number of ICE 1106 are specifically depicted in FIG. 11, itshould be appreciated that any number of ICE 1106 may be used in therotating disc 1103, without departing from the scope of the disclosure.Each ICE 1106 may be similar in construction to the ICE 100 describedabove with reference to FIG. 1, and configured to be either associatedor disassociated with a particular characteristic of the sample 202,such as is described above with reference to the first and second ICE302, 304 of FIG. 3 a. Moreover, each ICE may be either positivelycorrelated or negatively correlated as corresponding to thecharacteristic of interest in the sample 202.

In operation, the rotating disc 1103 rotates such that the one or moreICE 1106 may each be exposed to or otherwise optically interact with theoptically interacted radiation 206 for a distinct brief period of time.In at least one embodiment, however, the rotating disc 1103 may bearranged antecedent to the sample 202, and therefore the one or more ICE1106 may be exposed to or otherwise optically interact with theelectromagnetic radiation 204 for a brief period of time. Upon opticallyinteracting with the optically interacted radiation 206, each ICE 1106may be configured to produce an individual or combined beam of modifiedelectromagnetic radiation 1008 directed toward the detector 212.Moreover, as each individual ICE 1106 aligns with the opticallyinteracted light 206 to produce corresponding modified electromagneticradiations 1008, several distinct primary channels for conveying anddetecting light are generated, and at least one reference channel isgenerated that may operate substantially similarly to a primary channelsince an ICE 1106 is arranged therein as opposed to a traditionalneutral element.

Each individual or combined beam of modified electromagnetic radiation1008 may be detected by the detector 212 which may be configured to timemultiplex the modified electromagnetic radiation 1008 between thecombined or individually-detected beams in each primary and referencechannel. Consequently, the detector 212 receives a plurality of beams ofmodified electromagnetic radiation 1008 which may be computationallycombined by the detector 212 in order to provide an output in the formof a voltage that corresponds to the characteristic of the sample.Moreover, one or more of the ICE 1106 may be a neutral element orotherwise an aperture may be defined in the rotating disc 1103 andconfigured to provide a neutral signal to the detector 212, and therebyprovide a true reference channel, as generally described above withreference to FIG. 10. The neutral signal may be indicative of radiatingdeviations stemming from the electromagnetic radiation source 201, andthe detector 212 may be configured to computationally combine theneutral signal with the remaining beams of modified electromagneticradiation 1008 to compensate for electromagnetic radiating deviationsstemming from the electromagnetic radiation source 201, and therebyprovide a more accurate determination of the characteristic of thesample.

While the various embodiments disclosed herein provide that theelectromagnetic radiation source 201 is used to provide electromagneticradiation that optically interacts with the at least two ICEs, thoseskilled in the art will readily recognize that electromagnetic radiationmay be derived from the sample 202 itself, and otherwise derivedindependent of the electromagnetic radiation source 201. For example,various substances naturally radiate electromagnetic radiation that isable to optically interact with the at least two ICEs. In someembodiments, the sample 202 may be a blackbody radiating substanceconfigured to radiate heat that may optically interact with the at leasttwo ICEs. In other embodiments, the sample 202 may be radioactive orchemo-luminescent and therefore radiate electromagnetic radiation thatis able to optically interact with the at least two ICEs. In yet otherembodiments, the electromagnetic radiation may be induced from thesample 202 by being acted upon mechanically, magnetically, electrically,combinations thereof, or the like. For instance, in at least oneembodiment a voltage may be placed across the sample 202 in order toinduce the electromagnetic radiation. As a result, embodiments arecontemplated herein where the electromagnetic radiation source 201 isentirely omitted from the particular optical computing device.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered,combined, or modified and all such variations are considered within thescope and spirit of the present invention. While compositions andmethods are described in terms of “comprising,” “containing,” or“including” various components or steps, the compositions and methodscan also “consist essentially of” or “consist of” the various componentsand steps. All numbers and ranges disclosed above may vary by someamount. Whenever a numerical range with a lower limit and an upper limitis disclosed, any number and any included range falling within the rangeis specifically disclosed. In particular, every range of values (of theform, “from about a to about b,” or, equivalently, “from approximately ato b,” or, equivalently, “from approximately a-b”) disclosed herein isto be understood to set forth every number and range encompassed withinthe broader range of values. Also, the terms in the claims have theirplain, ordinary meaning unless otherwise explicitly and clearly definedby the patentee. Moreover, the indefinite articles “a” or “an,” as usedin the claims, are defined herein to mean one or more than one of theelement that it introduces. If there is any conflict in the usages of aword or term in this specification and one or more patent or otherdocuments that may be incorporated herein by reference, the definitionsthat are consistent with this specification should be adopted.

What is claimed is:
 1. A device, comprising: an electromagneticradiation source configured to optically interact with a sample having acharacteristic of interest; a first integrated computational elementarranged within a primary channel and configured to optically interactwith the electromagnetic radiation source and produce a first modifiedelectromagnetic radiation, wherein the first integrated computationalelement is configured to be positively or negatively correlated to thecharacteristic of interest; a second integrated computational elementarranged within a reference channel and configured to optically interactwith the electromagnetic radiation source and produce a second modifiedelectromagnetic radiation, wherein the second integrated computationalelement is configured to be positively or negatively correlated to thecharacteristic of interest; and a first detector arranged to receive thefirst and second modified electromagnetic radiations from the first andsecond integrated computational elements, respectively, and generate anoutput signal corresponding to the characteristic of the sample.
 2. Thedevice of claim 1, wherein the first integrated computational element isconfigured to be positively correlated to the characteristic of interestand the second integrated computational element is configured to benegatively correlated to the characteristic of interest.
 3. The deviceof claim 1, wherein the first integrated computational element isconfigured to be negatively correlated to the characteristic of interestand the second integrated computational element is configured to bepositively correlated to the characteristic of interest.
 4. The deviceof claim 1, wherein each of the first and second integratedcomputational elements is configured to be positively or negativelycorrelated to the characteristic of interest.
 5. The device of claim 1,wherein the first detector is a split detector comprising a firstdetector portion arranged in the primary channel to receive the firstmodified electromagnetic radiation and a second detector portionarranged in the reference channel to receive the second modifiedelectromagnetic radiation.
 6. The device of claim 5, wherein the splitdetector computationally combines the first and second modifiedelectromagnetic radiations to determine the characteristic of thesample.
 7. The device of claim 5, wherein the output signal comprises afirst output signal generated by the first detector portion and a secondoutput signal generated by the second detector portion, the first andsecond output signals being transmitted to and received by a signalprocessor configured to computationally combine the first and secondoutput signals to determine the characteristic of the sample.
 8. Thedevice of claim 1, further comprising a second detector arranged in asecond reference channel and configured to detect electromagneticradiation from the electromagnetic radiation source and thereby generatea compensating signal indicative of electromagnetic radiatingdeviations.
 9. The device of claim 8, further comprising a signalprocessor communicably coupled to the first and second detectors, thesignal processor being configured to receive and computationally combinethe output signal and the compensation signal to normalize the outputsignal.
 10. The device of claim 1, wherein the first and secondintegrated computational elements are coupled together to form amonolithic structure.
 11. The device of claim 1, wherein the first andsecond computational elements are arranged in series.
 12. The device ofclaim 1, wherein the first and second integrated computational elementsare arranged parallel relative to the other.
 13. The device of claim 1,wherein the first and second integrated computational elements areconfigured to be associated with the characteristic of the sample. 14.The device of claim 1, wherein at least one of the first and secondintegrated computational elements is configured to be disassociated withthe characteristic of the sample.
 15. The device of claim 1, furthercomprising a movable assembly configured for rotation, the first andsecond integrated computational elements being radially disposed withinthe movable assembly for rotation therewith, wherein the primary channelis generated as the first integrated computational element aligns withthe electromagnetic radiation source and the first detector, and thereference channel is generated as the second integrated computationalelement aligns with the electromagnetic radiation source and the firstdetector.
 16. The device of claim 1, wherein the first and secondintegrated computational elements are laterally arranged upon a movableassembly such that the first and second integrated computationalelements optically interact with electromagnetic radiation individually,wherein the primary channel is generated as the first integratedcomputational element aligns with the electromagnetic radiation sourceand the first detector, and the reference channel is generated as thesecond integrated computational element aligns with the electromagneticradiation source and the first detector.
 17. The device of claim 16,wherein the movable assembly is configured for lateral or verticaloscillation.
 18. A device, comprising: an electromagnetic radiationsource configured to optically interact with a sample having acharacteristic of interest; a first integrated computational elementarranged within a primary channel and configured to optically interactwith the electromagnetic radiation source and produce a first modifiedelectromagnetic radiation, wherein the first integrated computationalelement is configured to be positively or negatively correlated to thecharacteristic of interest; a second integrated computational elementarranged within a second channel and configured to optically interactwith the electromagnetic radiation source and produce a second modifiedelectromagnetic radiation, wherein the second integrated computationalelement is configured to be positively or negatively correlated to thecharacteristic of interest; a first detector arranged to receive thefirst modified electromagnetic radiation and generate a first outputsignal; a second detector arranged to receive the second modifiedelectromagnetic radiation and generate a second output signal; and asignal processor configured to receive and computationally combine thefirst and second output signals to determine the characteristic ofinterest of the sample.
 19. The device of claim 18, wherein the firstintegrated computational element is configured to be positivelycorrelated to the characteristic of interest and the second integratedcomputational element is configured to be negatively correlated to thecharacteristic of interest.
 20. The device of claim 18, wherein thefirst integrated computational element is configured to be negativelycorrelated to the characteristic of interest and the second integratedcomputational element is configured to be positively correlated to thecharacteristic of interest.
 21. The device of claim 18, wherein each ofthe first and second integrated computational elements is configured tobe positively or negatively correlated to the characteristic ofinterest.
 22. The device of claim 18, further comprising a beam splitterconfigured to produce a first beam of light directed toward the firstintegrated computational element and a second beam of light directedtoward the second integrated computational element.
 23. The device ofclaim 18, further comprising a second detector arranged in a secondreference channel and configured to detect electromagnetic radiationfrom the electromagnetic radiation source and thereby generate acompensating signal indicative of electromagnetic radiating deviations.24. The device of claim 23, wherein the signal processor is configuredto receive and computationally combine the output signal and thecompensation signal to normalize the output signal.
 25. The device ofclaim 18, wherein the first and second integrated computational elementsare coupled together to form a monolithic structure.
 26. The device ofclaim 18, wherein the first and second computational elements arearranged in series.
 27. The device of claim 18, wherein the first andsecond integrated computational elements are arranged parallel relativeto the other.
 28. The device of claim 18, wherein the first and secondintegrated computational elements are configured to be associated withthe characteristic of the sample.
 29. The device of claim 18, wherein atleast one of the first and second integrated computational elements isconfigured to be disassociated with the characteristic of the sample.